feat(mini-apps): open built app in middle pane from chat

After the copilot builds + verifies + populates an app, it opens it in the
middle pane under Mini Apps / <title>, with an 'Opened <app>' card in chat.

- app-navigation: new open-app action (reads manifest title)
- renderer: pending-nav opens the Mini Apps view with the app pre-selected;
  MiniAppsView accepts initialAppId/initialVersion
- chat: open-app app-action card labels
- build-mini-app skill: finalize step opens the app once data is populated

apps/x/apps/renderer/src/App.tsx

@@ -2001,6 +2001,9 @@ function App() {
   }>>([])
   const [bgTaskInitialSlug, setBgTaskInitialSlug] = useState<string | null>(null)
   const [bgTaskSlugVersion, setBgTaskSlugVersion] = useState(0)
+  // Mini App to auto-open in the Mini Apps view (set by app-navigation open-app).
+  const [appInitialId, setAppInitialId] = useState<string | null>(null)
+  const [appIdVersion, setAppIdVersion] = useState(0)
 
   const loadBgTaskSummaries = useCallback(async () => {
     try {
@@ -4506,6 +4509,13 @@ function App() {
           void navigateToView({ type: 'file', path: BASES_DEFAULT_TAB_PATH })
         }
         break
+      case 'open-app':
+        if (result.appId) {
+          setAppInitialId(result.appId as string)
+          setAppIdVersion((v) => v + 1)
+          openAppsView()
+        }
+        break
       case 'update-base-view': {
         // Navigate to bases if not already there
         const targetPath = selectedPath && isBaseFilePath(selectedPath) ? selectedPath : BASES_DEFAULT_TAB_PATH
@@ -5983,7 +5993,7 @@ function App() {
                 </div>
               ) : isAppsOpen ? (
                 <div className="flex-1 min-h-0 flex flex-col overflow-hidden">
-                  <MiniAppsView />
+                  <MiniAppsView initialAppId={appInitialId} initialVersion={appIdVersion} />
                 </div>
               ) : isEmailOpen ? (
                 <div className="flex-1 min-h-0 flex flex-col overflow-hidden">

apps/x/apps/renderer/src/components/mini-apps-view.tsx

@@ -153,10 +153,15 @@ function Card({ app, index, onOpen }: { app: miniApp.MiniAppManifest; index: num
   )
 }
 
-export function MiniAppsView() {
-  const [selectedId, setSelectedId] = useState<string | null>(null)
+export function MiniAppsView({ initialAppId, initialVersion }: { initialAppId?: string | null; initialVersion?: number } = {}) {
+  const [selectedId, setSelectedId] = useState<string | null>(initialAppId ?? null)
   const [manifests, setManifests] = useState<miniApp.MiniAppManifest[]>([])
 
+  // Open a specific app when asked from outside (app-navigation open-app).
+  useEffect(() => {
+    if (initialAppId) setSelectedId(initialAppId)
+  }, [initialAppId, initialVersion])
+
   // List apps installed under ~/.rowboat/apps. Apps are created there by the
   // copilot builder (or placed manually); none are bundled in the repo.
   useEffect(() => {

apps/x/apps/renderer/src/lib/chat-conversation.ts

@@ -210,6 +210,7 @@ export const getAppActionCardData = (tool: ToolCall): AppActionCardData | null =
     switch (action) {
       case 'open-note': return { action, label: `Opening ${(input.path as string || '').split('/').pop()?.replace(/\.md$/, '') || 'note'}...` }
       case 'open-view': return { action, label: `Opening ${input.view} view...` }
+      case 'open-app': return { action, label: `Opening ${input.appId || 'app'}...` }
       case 'update-base-view': return { action, label: 'Updating view...' }
       case 'create-base': return { action, label: `Creating "${input.name}"...` }
       case 'get-base-state': return null // renders as normal tool block
@@ -225,6 +226,8 @@ export const getAppActionCardData = (tool: ToolCall): AppActionCardData | null =
     }
     case 'open-view':
       return { action: 'open-view', label: `Opened ${result.view} view` }
+    case 'open-app':
+      return { action: 'open-app', label: `Opened ${result.appName || result.appId || 'app'}` }
     case 'update-base-view':
       return {
         action: 'update-base-view',

apps/x/packages/core/src/application/assistant/skills/build-mini-app/skill.ts

@@ -95,10 +95,14 @@ manifest's \`agent\` field to the task's slug. Give the task a sensible trigger
 
 ## 5. Finalize
 
-Call \`mini-app-install\` with the manifest + html (+ optional seed data). Then
-confirm to the user, and ideally open it so they see it populate. For agent-backed
-apps, trigger the agent once (\`run-background-task-agent\`) so \`data.json\` exists
-immediately instead of waiting for the first scheduled run.
+Call \`mini-app-install\` with the manifest + html (+ optional seed data). For
+agent-backed apps, trigger the agent once (\`run-background-task-agent\`) so
+\`data.json\` exists immediately instead of waiting for the first scheduled run.
+
+Then **open it for the user**: call \`app-navigation\` with
+\`{ action: "open-app", appId: "<id>" }\`. This opens the app in the middle pane
+(under Mini Apps / its title) and shows an "Opened <app>" card in the chat. Only
+do this once the app is installed AND its data is populated, so it renders ready.
 
 ## Manifest schema (manifest.json)
 

apps/x/packages/core/src/application/lib/builtin-tools.ts

@@ -1068,9 +1068,11 @@ export const BuiltinTools: z.infer<typeof BuiltinToolsSchema> = {
     'app-navigation': {
         description: 'Control the app UI - navigate to notes, switch views, filter/search the knowledge base, and manage saved views.',
         inputSchema: z.object({
-            action: z.enum(["open-note", "open-view", "update-base-view", "get-base-state", "create-base"]).describe("The navigation action to perform"),
+            action: z.enum(["open-note", "open-view", "open-app", "update-base-view", "get-base-state", "create-base"]).describe("The navigation action to perform"),
             // open-note
             path: z.string().optional().describe("Knowledge file path for open-note, e.g. knowledge/People/John.md"),
+            // open-app
+            appId: z.string().optional().describe("Mini App id (folder name under ~/.rowboat/apps) for open-app — opens it in the middle pane under Mini Apps."),
             // open-view
             view: z.enum(["bases", "graph"]).optional().describe("Which view to open (for open-view action)"),
             // update-base-view
@@ -1118,6 +1120,20 @@ export const BuiltinTools: z.infer<typeof BuiltinToolsSchema> = {
                     return { success: true, action: 'open-view', view };
                 }
 
+                case 'open-app': {
+                    const appId = input.appId as string;
+                    if (!appId) return { success: false, error: 'open-app requires appId' };
+                    let appName = appId;
+                    try {
+                        const raw = await fs.readFile(path.join(WorkDir, 'apps', appId, 'manifest.json'), 'utf-8');
+                        const m = JSON.parse(raw) as { title?: string };
+                        if (m.title) appName = m.title;
+                    } catch {
+                        return { success: false, error: `Mini App not found: ${appId}` };
+                    }
+                    return { success: true, action: 'open-app', appId, appName };
+                }
+
                 case 'update-base-view': {
                     const updates: Record<string, unknown> = {};
                     if (input.filters) updates.filters = input.filters;