feat(studio): App Builder nav entry — pillar builder joins the login journey (#2531)

Add an App Builder entry (componentRef studio:builder, first in Overview) to the
Studio app navigation. The console binds studio:builder to the builder landing
page (objectui#2175), making the pillar application builder reachable from login
(Home → Studio → App Builder → pick/create a writable base → /studio/:pkg/data)
instead of being a URL-only surface.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: os-zhuang

.changeset/studio-app-builder-nav.md

@@ -0,0 +1,11 @@
+---
+"@objectstack/platform-objects": patch
+---
+
+feat(studio): "App Builder" navigation entry — the pillar builder joins the journey
+
+The Studio app's Overview group gains an **App Builder** entry (componentRef
+`studio:builder`, bound by the console to the builder landing page). This makes the
+pillar application builder reachable from the moment a user logs in — Home → Studio
+→ App Builder → pick/create a writable base package → the full-screen builder at
+`/studio/:packageId/:tab` — instead of being a URL-only surface.

packages/platform-objects/src/apps/studio.app.ts

@@ -84,6 +84,19 @@ export const STUDIO_APP: App = {
       label: 'Overview',
       icon: 'layout-dashboard',
       children: [
+        {
+          // The application builder's front door (ADR-0080/0084): pick or
+          // create a writable base package, then design in the full-screen
+          // pillar builder (/studio/:packageId/:tab). The console binds
+          // `studio:builder` to the BuilderLanding page — this makes the
+          // builder reachable from login (Home → Studio → App Builder)
+          // instead of being a URL-only surface.
+          id: 'nav_app_builder',
+          type: 'component',
+          label: 'App Builder',
+          componentRef: 'studio:builder',
+          icon: 'hammer',
+        },
         {
           id: 'nav_metadata_directory',
           type: 'component',