mesh: carry gateway_domain so peers can launch remote apps

The mesh payload didn't include a node's acme domain, so a peer had no way
to build launch URLs for another machine's exposed apps. Publish
gateway_domain in the MQTT registry payload and surface it per-deployment on
/mesh/deployments as `domain`. The dashboard palette and System Map now build
`https://<subdomain>.<domain>` for remote http-exposed apps (references use
their base_url), making primer's apps launchable from civil.

app/src/components/CommandPalette.tsx

@@ -78,12 +78,20 @@ function PaletteBody({ onClose }: { onClose: () => void }) {
       })
     }
     for (const md of mesh?.deployments ?? []) {
+      // A remote app is launchable at <subdomain>.<node-domain> when the node has an
+      // acme domain and the app is http-exposed (subdomain set); references carry base_url.
+      const remoteLaunch =
+        md.kind === "reference"
+          ? (md.base_url ?? undefined)
+          : md.subdomain && md.domain
+            ? `https://${md.subdomain}.${md.domain}`
+            : undefined
       out.push({
         id: `${md.node}/${md.name}`,
         name: md.name,
         kind: md.kind,
         machine: md.node,
-        launchUrl: undefined, // remote launch URL isn't in the mesh payload yet
+        launchUrl: remoteLaunch,
         detailPath: `/node/${md.node}`,
         mapNodeId: `__remote_${md.node}_${md.name}__`,
       })

app/src/pages/SystemMap.tsx

@@ -324,11 +324,18 @@ function ExternalNode({ data }: NodeProps) {
 // A deployment on another castle node (mesh-discovered). Read-only — you manage
 // remote deployments from that node.
 function RemoteNode({ data }: NodeProps) {
-  const d = data as { label: string; kind: string; sub?: string; focusDim?: boolean; focused?: boolean }
+  const d = data as {
+    label: string
+    kind: string
+    sub?: string
+    launchUrl?: string
+    focusDim?: boolean
+    focused?: boolean
+  }
   const color = KIND_COLOR[d.kind] ?? "#8b949e"
   return (
     <div
-      className="flex w-[132px] items-stretch overflow-hidden rounded-md border border-dashed bg-[var(--card)] text-xs"
+      className="group relative flex w-[132px] items-stretch overflow-hidden rounded-md border border-dashed bg-[var(--card)] text-xs"
       style={{
         borderColor: color,
         opacity: d.focusDim ? 0.12 : 0.9,
@@ -336,6 +343,18 @@ function RemoteNode({ data }: NodeProps) {
       }}
       title="remote (on another node)"
     >
+      {d.launchUrl && (
+        <a
+          href={d.launchUrl}
+          target="_blank"
+          rel="noreferrer"
+          className="absolute right-0.5 top-0.5 z-10 rounded bg-[var(--card)]/80 p-0.5 text-[var(--muted)] opacity-0 hover:text-[var(--primary)] group-hover:opacity-100"
+          title={`Launch ${d.launchUrl}`}
+          onClick={(e) => e.stopPropagation()}
+        >
+          <ExternalLink size={12} />
+        </a>
+      )}
       <div className="w-1 shrink-0" style={{ background: color }} />
       <div className="min-w-0 flex-1 px-2 py-1">
         <div className="truncate text-[var(--card-foreground)]" title={d.label}>
@@ -476,6 +495,14 @@ export function SystemMapPage() {
       return undefined
     }
 
+    // Remote launch: <subdomain>.<node-domain>, using the node's own acme domain
+    // carried in the mesh payload. References launch at their base_url.
+    const remoteLaunchOf = (md: MeshDeployment): string | undefined => {
+      if (md.kind === "reference") return md.base_url ?? undefined
+      if (md.subdomain && md.domain) return `https://${md.subdomain}.${md.domain}`
+      return undefined
+    }
+
     // Consumption of an external `reference` renders as a chip on the consumer (not
     // a long cross-map edge). Collect them here, keyed by the consuming deployment.
     // A job shows its cron; everything else prefers its declared socket, else its
@@ -658,6 +685,7 @@ export function SystemMapPage() {
             label: md.name,
             kind: md.kind,
             sub: md.endpoints[0] ? `:${md.endpoints[0].port}` : undefined,
+            launchUrl: remoteLaunchOf(md),
           },
         })
       }
@@ -870,7 +898,7 @@ export function SystemMapPage() {
         capsConsumes: [],
         reach: null,
         exposable: false,
-        launchUrl: ri.md.base_url ?? undefined,
+        launchUrl: remoteLaunchOf(ri.md),
       })
 
     return { nodes, edges, kindOf, reachOf, consumes, consumedBy, meta }

app/src/types/index.ts

@@ -168,6 +168,7 @@ export interface MeshDeployment {
   name: string
   kind: string
   node: string // the remote hostname
+  domain: string | null // the node's gateway acme domain — for <subdomain>.<domain> launch URLs
   port: number | null
   base_url: string | null
   subdomain: string | null

castle-api/src/castle_api/mqtt_client.py

@@ -37,6 +37,9 @@ def _registry_to_json(registry: NodeRegistry) -> str:
         "node": {
             "hostname": registry.node.hostname,
             "gateway_port": registry.node.gateway_port,
+            # acme domain — lets peers build launch URLs (<subdomain>.<gateway_domain>)
+            # for this node's exposed apps. Omitted when the node has no domain.
+            "gateway_domain": registry.node.gateway_domain,
         },
         "deployed": {},
     }
@@ -83,6 +86,7 @@ def _json_to_registry(payload: str) -> NodeRegistry:
         hostname=node_data.get("hostname", ""),
         castle_root=node_data.get("castle_root"),
         gateway_port=node_data.get("gateway_port", 9000),
+        gateway_domain=node_data.get("gateway_domain"),
     )
     deployed: dict[str, Deployment] = {}
     for key, comp_data in data.get("deployed", {}).items():

castle-api/src/castle_api/nodes.py

@@ -115,16 +115,18 @@ def _endpoints_of_registry(d: object) -> list[dict]:
 def mesh_deployments() -> dict:
     """Flattened remote (mesh-discovered) deployments with derived endpoints — the
     data the System Map needs to render other machines. Local node excluded (it's
-    already in /graph). Cross-node dependency *edges* need `requires` in the mesh
-    payload, which the registry doesn't carry yet."""
+    already in /graph). Each entry carries its node's `domain` (gateway acme domain)
+    so peers can build launch URLs `<subdomain>.<domain>` for exposed apps."""
     out: list[dict] = []
     for hostname, remote in mesh_state.all_nodes(include_stale=True).items():
+        domain = getattr(remote.registry.node, "gateway_domain", None)
         for _kind, name, d in remote.registry.all():
             out.append(
                 {
                     "name": name,
                     "kind": d.kind,
                     "node": hostname,
+                    "domain": domain,
                     "port": d.port,
                     "base_url": getattr(d, "base_url", None),
                     "subdomain": d.subdomain,