feat: isolate Claude and Codex session sources

Persist platform_source across session creation, transcript ingestion, API query paths, and viewer state so Claude and Codex data can coexist without bleeding into each other.

- add platform-source normalization helpers and persist platform_source in sdk_sessions via migration 24 with backfill and indexing
- thread platformSource through CLI hooks, transcript processing, context generation, pagination, search routes, SSE payloads, and session management
- expose source-aware project catalogs, viewer tabs, context preview selectors, and source badges for observations, prompts, and summaries
- start the transcript watcher from the worker for transcript-based clients and preserve platform source during Codex ingestion
- auto-start the worker from the MCP server for MCP-only clients and tighten stdio-driven cleanup during shutdown
- keep createSDKSession backward compatible with existing custom-title callers while allowing explicit platform source forwarding

src/services/worker/http/routes/ViewerRoutes.ts

@@ -76,11 +76,13 @@ export class ViewerRoutes extends BaseRouteHandler {
     // Add client to broadcaster
     this.sseBroadcaster.addClient(res);
 
-    // Send initial_load event with projects list
-    const allProjects = this.dbManager.getSessionStore().getAllProjects();
+    // Send initial_load event with project/source catalog
+    const projectCatalog = this.dbManager.getSessionStore().getProjectCatalog();
     this.sseBroadcaster.broadcast({
       type: 'initial_load',
-      projects: allProjects,
+      projects: projectCatalog.projects,
+      sources: projectCatalog.sources,
+      projectsBySource: projectCatalog.projectsBySource,
       timestamp: Date.now()
     });