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/BaseRouteHandler.ts

@@ -11,6 +11,7 @@
 
 import { Request, Response } from 'express';
 import { logger } from '../../../utils/logger.js';
+import { AppError } from '../../server/ErrorHandler.js';
 
 export abstract class BaseRouteHandler {
   /**
@@ -80,7 +81,18 @@ export abstract class BaseRouteHandler {
   protected handleError(res: Response, error: Error, context?: string): void {
     logger.failure('WORKER', context || 'Request failed', {}, error);
     if (!res.headersSent) {
-      res.status(500).json({ error: error.message });
+      const statusCode = error instanceof AppError ? error.statusCode : 500;
+      const response: Record<string, unknown> = { error: error.message };
+
+      if (error instanceof AppError && error.code) {
+        response.code = error.code;
+      }
+
+      if (error instanceof AppError && error.details !== undefined) {
+        response.details = error.details;
+      }
+
+      res.status(statusCode).json(response);
     }
   }
 }