app: Add-program flow with server-side filesystem picker

Register an existing repo as a program from the /programs page — the web
equivalent of `castle program add`. An inline form with an editable,
autocompleting path bar browses the *server's* filesystem (a browser's own
file dialog only sees the client machine) and also accepts a git URL.

- core: extract the adopt logic (target parsing, stack/command detection,
  ProgramSpec build) into castle_core.adopt so the CLI and API share it; the
  CLI's add.py now delegates to it.
- castle-api: GET /fs/browse (directory listing, per-entry stat errors skipped
  so one unreadable child can't 403 the dir) and POST /programs/adopt.
- app: AddProgramForm + Add-program button on the Programs page; useBrowse /
  useAdoptProgram hooks.

Also tidy ProgramCard: deployments render below the description, and the
deployment name label is hidden when it matches the program title.

app/src/pages/Programs.tsx

@@ -1,17 +1,41 @@
+import { useState } from "react"
+import { Plus } from "lucide-react"
 import { usePrograms } from "@/services/api/hooks"
 import { ProgramList } from "@/components/ProgramList"
 import { MonorepoBanner } from "@/components/MonorepoBanner"
 import { PageHeader } from "@/components/PageHeader"
+import { AddProgramForm } from "@/components/AddProgramForm"
 
 export function Programs() {
   const { data: programs, isLoading } = usePrograms()
+  const [adding, setAdding] = useState(false)
 
   return (
     <div className="max-w-6xl mx-auto px-6 py-8">
-      <PageHeader title="Programs" subtitle="Software catalog" />
+      <PageHeader
+        title="Programs"
+        subtitle="Software catalog"
+        actions={
+          <button
+            onClick={() => setAdding((a) => !a)}
+            className="flex items-center gap-1 px-3 py-1.5 text-sm rounded border border-[var(--border)] text-[var(--muted)] hover:text-[var(--foreground)] hover:border-[var(--primary)] transition-colors"
+          >
+            <Plus size={14} /> Add program
+          </button>
+        }
+      />
 
       <MonorepoBanner />
 
+      {adding && (
+        <div className="mb-6 max-w-2xl">
+          <AddProgramForm
+            existingNames={(programs ?? []).map((p) => p.id)}
+            onCancel={() => setAdding(false)}
+          />
+        </div>
+      )}
+
       {isLoading ? (
         <p className="text-[var(--muted)]">Loading...</p>
       ) : programs && programs.length > 0 ? (