ui: field help text + editable program commands

- Add a 'hint' to the shared Field/TextField; annotate the config forms with
  short, accurate descriptions of each field:
  - program: source (working copy castle builds from), behavior (tool/daemon/
    frontend), stack (optional toolchain template), repo/ref (for clone),
    system deps (listed for reference, NOT auto-installed), commands.
  - service: port (listened-on, health-checked, proxied; map via ${port}),
    health path, proxy path vs proxy host, runs.
  - job: schedule (cron → systemd timer), runs.
- ProgramFields: the Commands section is now editable (build/test/lint/
  type-check/run), so a program with no stack can declare its own dev verbs
  by hand — a declared command overrides the stack default. Verified the
  commands/build shape round-trips through the config API.

App builds clean.

app/src/components/detail/JobFields.tsx

@@ -58,8 +58,16 @@ export function JobFields({ job, onSave, onDelete }: Props) {
   return (
     <div className="space-y-4">
       <TextField label="Description" value={description} onChange={setDescription} />
-      <TextField label="Schedule" value={schedule} onChange={setSchedule} width="w-48" mono placeholder="0 2 * * *" />
-      <Field label="Runs">
+      <TextField
+        label="Schedule"
+        value={schedule}
+        onChange={setSchedule}
+        width="w-48"
+        mono
+        placeholder="0 2 * * *"
+        hint="Cron expression — castle generates a systemd timer that runs the job on this schedule."
+      />
+      <Field label="Runs" hint="The console script or command the job runs on each tick, then exits.">
         <span className="text-sm font-mono text-[var(--muted)]">{runnerLabel(runner)} &middot; </span>
         <input
           value={runTarget}

app/src/components/detail/ProgramFields.tsx

@@ -5,13 +5,20 @@ import { Field, TextField, FormFooter } from "./fields"
 const SELECT =
   "bg-black/30 border border-[var(--border)] rounded px-3 py-1.5 text-sm focus:outline-none focus:border-[var(--primary)]"
 
+// Verbs the commands editor exposes. `build` lives in `build.commands`; the rest
+// in `commands`. A declared command overrides the stack default (or supplies the
+// verb when there's no stack).
+const VERBS = ["build", "test", "lint", "type-check", "run"]
+
 interface Props {
   program: ProgramDetail
   onSave: (name: string, config: Record<string, unknown>) => Promise<void>
   onDelete?: (name: string) => Promise<void>
 }
 
-/** Edit a program's catalog config (source identity), not how it's deployed. */
+type Obj = Record<string, unknown>
+
+/** Edit a program's catalog config (its source identity), not how it's deployed. */
 export function ProgramFields({ program, onSave, onDelete }: Props) {
   const m = program.manifest
   const [saving, setSaving] = useState(false)
@@ -26,11 +33,24 @@ export function ProgramFields({ program, onSave, onDelete }: Props) {
   const [ref, setRef] = useState((m.ref as string) ?? "")
   const [deps, setDeps] = useState(((m.system_dependencies as string[]) ?? []).join(", "))
 
+  const readVerb = (verb: string): string => {
+    if (verb === "build") {
+      const c = (m.build as { commands?: string[][] } | undefined)?.commands
+      return (c?.[0] ?? []).join(" ")
+    }
+    const cmds = (m.commands as Record<string, string[][]> | undefined) ?? {}
+    const key = verb === "type-check" && !cmds["type-check"] ? "type_check" : verb
+    return (cmds[key]?.[0] ?? []).join(" ")
+  }
+  const [cmds, setCmds] = useState<Record<string, string>>(() =>
+    Object.fromEntries(VERBS.map((v) => [v, readVerb(v)])),
+  )
+
   const handleSave = async () => {
     setSaving(true)
     setSaved(false)
     try {
-      const config: Record<string, unknown> = { ...m }
+      const config: Obj = { ...m }
       delete config.id
       config.description = description || undefined
       config.source = source || undefined
@@ -39,10 +59,20 @@ export function ProgramFields({ program, onSave, onDelete }: Props) {
       config.version = version || undefined
       config.repo = repo || undefined
       config.ref = ref || undefined
-      config.system_dependencies = deps
-        .split(",")
-        .map((d) => d.trim())
-        .filter(Boolean)
+      config.system_dependencies = deps.split(",").map((d) => d.trim()).filter(Boolean)
+
+      const commands: Record<string, string[][]> = {}
+      let buildArgv: string[][] | null = null
+      for (const v of VERBS) {
+        const s = (cmds[v] ?? "").trim()
+        if (!s) continue
+        const argv: string[][] = [s.split(/\s+/)]
+        if (v === "build") buildArgv = argv
+        else commands[v] = argv
+      }
+      if (buildArgv) config.build = { ...((m.build as Obj) ?? {}), commands: buildArgv }
+      config.commands = Object.keys(commands).length ? commands : undefined
+
       await onSave(program.id, config)
       setSaved(true)
       setTimeout(() => setSaved(false), 2000)
@@ -53,9 +83,24 @@ export function ProgramFields({ program, onSave, onDelete }: Props) {
 
   return (
     <div className="space-y-4">
-      <TextField label="Description" value={description} onChange={setDescription} />
-      <TextField label="Source" value={source} onChange={setSource} mono placeholder="/data/repos/my-prog" />
-      <Field label="Behavior">
+      <TextField
+        label="Description"
+        value={description}
+        onChange={setDescription}
+        hint="One-line summary. A service or job running this program inherits it when it has none of its own."
+      />
+      <TextField
+        label="Source"
+        value={source}
+        onChange={setSource}
+        mono
+        placeholder="/data/repos/my-prog"
+        hint="The working copy on disk. Castle runs dev verbs and builds here. Absolute path, or repo:<name> for castle's own programs."
+      />
+      <Field
+        label="Behavior"
+        hint="What this program is. tool = a CLI you invoke; daemon = a long-running server; frontend = a web UI. Drives how it activates and deploys."
+      >
         <select value={behavior} onChange={(e) => setBehavior(e.target.value)} className={`w-48 ${SELECT}`}>
           <option value="">(none)</option>
           <option value="tool">tool</option>
@@ -63,7 +108,10 @@ export function ProgramFields({ program, onSave, onDelete }: Props) {
           <option value="frontend">frontend</option>
         </select>
       </Field>
-      <Field label="Stack">
+      <Field
+        label="Stack"
+        hint="Optional toolchain template — seeds default dev-verb commands and a scaffold for new code. Leave empty and declare commands below to wire in any repo."
+      >
         <select value={stack} onChange={(e) => setStack(e.target.value)} className={`w-48 ${SELECT}`}>
           <option value="">(none)</option>
           <option value="python-cli">python-cli</option>
@@ -71,23 +119,49 @@ export function ProgramFields({ program, onSave, onDelete }: Props) {
           <option value="react-vite">react-vite</option>
         </select>
       </Field>
-      <TextField label="Version" value={version} onChange={setVersion} width="w-32" />
-      <TextField label="Repo" value={repo} onChange={setRepo} mono placeholder="https://github.com/me/x.git" />
-      <TextField label="Ref" value={ref} onChange={setRef} width="w-48" placeholder="branch / tag / commit" />
-      <TextField label="System deps" value={deps} onChange={setDeps} placeholder="pandoc, poppler-utils" />
+      <TextField label="Version" value={version} onChange={setVersion} width="w-32" hint="Optional metadata." />
+      <TextField
+        label="Repo"
+        value={repo}
+        onChange={setRepo}
+        mono
+        placeholder="https://github.com/me/x.git"
+        hint="Git URL so 'castle program clone' can fetch the source on a fresh machine. An existing working copy at Source takes precedence."
+      />
+      <TextField
+        label="Ref"
+        value={ref}
+        onChange={setRef}
+        width="w-48"
+        placeholder="branch / tag / commit"
+        hint="Optional ref to clone (branch, tag, or commit)."
+      />
+      <TextField
+        label="System deps"
+        value={deps}
+        onChange={setDeps}
+        placeholder="pandoc, poppler-utils"
+        hint="OS packages the program needs. Listed for reference — castle does not install them."
+      />
 
-      {program.commands && Object.keys(program.commands).length > 0 && (
-        <Field label="Commands">
-          <div className="space-y-1 pt-1.5">
-            {Object.entries(program.commands).map(([verb, cmds]) => (
-              <div key={verb} className="flex gap-2 text-xs">
-                <span className="text-[var(--muted)] w-20 shrink-0">{verb}</span>
-                <span className="font-mono break-all">{cmds.map((a) => a.join(" ")).join(" && ")}</span>
-              </div>
-            ))}
-          </div>
-        </Field>
-      )}
+      <Field
+        label="Commands"
+        hint="How to build/test/lint/run this program. A declared command overrides the stack default — and is how a program with no stack gets its dev verbs. One argv per line (e.g. ruff check .)."
+      >
+        <div className="space-y-1.5 pt-1.5">
+          {VERBS.map((verb) => (
+            <div key={verb} className="flex items-center gap-2">
+              <span className="text-xs text-[var(--muted)] w-20 shrink-0 font-mono">{verb}</span>
+              <input
+                value={cmds[verb] ?? ""}
+                onChange={(e) => setCmds((c) => ({ ...c, [verb]: e.target.value }))}
+                placeholder={stack ? "(stack default)" : "—"}
+                className="flex-1 bg-black/30 border border-[var(--border)] rounded px-2 py-1 text-xs font-mono focus:outline-none focus:border-[var(--primary)]"
+              />
+            </div>
+          ))}
+        </div>
+      </Field>
 
       <FormFooter
         saving={saving}

app/src/components/detail/ServiceFields.tsx

@@ -88,7 +88,10 @@ export function ServiceFields({ service, onSave, onDelete }: Props) {
   return (
     <div className="space-y-4">
       <TextField label="Description" value={description} onChange={setDescription} />
-      <Field label="Runs">
+      <Field
+        label="Runs"
+        hint="The console script (python runner) or command this service executes."
+      >
         <span className="text-sm font-mono text-[var(--muted)]">{runnerLabel(runner)} &middot; </span>
         <input
           value={runProgram}
@@ -96,10 +99,41 @@ export function ServiceFields({ service, onSave, onDelete }: Props) {
           className="w-56 bg-black/30 border border-[var(--border)] rounded px-2 py-1 text-xs font-mono focus:outline-none focus:border-[var(--primary)]"
         />
       </Field>
-      <TextField label="Port" value={port} onChange={setPort} width="w-32" mono placeholder="9001" />
-      <TextField label="Health path" value={health} onChange={setHealth} width="w-48" mono placeholder="/health" />
-      <TextField label="Proxy path" value={proxyPath} onChange={setProxyPath} width="w-48" mono placeholder="/my-service" />
-      <TextField label="Proxy host" value={proxyHost} onChange={setProxyHost} mono placeholder="my-service.lan" />
+      <TextField
+        label="Port"
+        value={port}
+        onChange={setPort}
+        width="w-32"
+        mono
+        placeholder="9001"
+        hint="The port the service listens on. Castle health-checks and proxies this port; map it to the program's own var with ${port} in Environment."
+      />
+      <TextField
+        label="Health path"
+        value={health}
+        onChange={setHealth}
+        width="w-48"
+        mono
+        placeholder="/health"
+        hint="HTTP path castle polls to report up/down."
+      />
+      <TextField
+        label="Proxy path"
+        value={proxyPath}
+        onChange={setProxyPath}
+        width="w-48"
+        mono
+        placeholder="/my-service"
+        hint="Gateway prefix — reachable at gateway:9000<path>/ (reverse-proxied to the port)."
+      />
+      <TextField
+        label="Proxy host"
+        value={proxyHost}
+        onChange={setProxyHost}
+        mono
+        placeholder="my-service.lan"
+        hint="Optional: route a whole hostname to this service instead of a path (lets a root-based app serve unchanged)."
+      />
       {envEditor}
       <FormFooter
         saving={saving}

app/src/components/detail/fields.tsx

@@ -5,11 +5,22 @@ import { SecretsEditor } from "@/components/SecretsEditor"
 const INPUT =
   "bg-black/30 border border-[var(--border)] rounded px-3 py-1.5 text-sm focus:outline-none focus:border-[var(--primary)]"
 
-export function Field({ label, children }: { label: string; children: React.ReactNode }) {
+export function Field({
+  label,
+  children,
+  hint,
+}: {
+  label: string
+  children: React.ReactNode
+  hint?: string
+}) {
   return (
     <div className="flex items-start gap-4">
       <label className="w-32 shrink-0 text-sm font-medium pt-1.5">{label}</label>
-      <div className="flex-1">{children}</div>
+      <div className="flex-1">
+        {children}
+        {hint && <p className="text-xs text-[var(--muted)] mt-1 leading-snug">{hint}</p>}
+      </div>
     </div>
   )
 }
@@ -21,6 +32,7 @@ export function TextField({
   placeholder,
   mono,
   width,
+  hint,
 }: {
   label: string
   value: string
@@ -28,9 +40,10 @@ export function TextField({
   placeholder?: string
   mono?: boolean
   width?: string
+  hint?: string
 }) {
   return (
-    <Field label={label}>
+    <Field label={label} hint={hint}>
       <input
         value={value}
         onChange={(e) => onChange(e.target.value)}