feat: dev env bootstrap, deferred sessions, and mock agent fallback

- Add dotenv loader for NODE_ENV=development with .env.development.example
- Add factory self-hosting deployment docs
- Defer agent session creation in handoff init (create on first prompt)
- Fall back to mock agent when Claude/Codex credentials are missing
- Replace stub mock agent launcher with real ACP JSON-RPC Node.js script
- Fix React useEffect dependency array in org settings
- Clean up tracked .context cache/temp files

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

factory/packages/frontend/src/components/mock-onboarding.tsx

@@ -636,7 +636,12 @@ export function MockOrganizationSettingsPage({ organization }: { organization: F
     setDisplayName(organization.settings.displayName);
     setSlug(organization.settings.slug);
     setPrimaryDomain(organization.settings.primaryDomain);
-  }, [organization]);
+  }, [
+    organization.id,
+    organization.settings.displayName,
+    organization.settings.slug,
+    organization.settings.primaryDomain,
+  ]);
 
   return (
     <PageShell