fix: resolve orphaned subprocesses and Chroma HTTP regressions

- Add subprocess cleanup after SDK query loop completes, using existing
  ProcessRegistry infrastructure (getProcessBySession + ensureProcessExit)
- Replace npx-based Chroma binary spawning with absolute path resolution
  via require.resolve, falling back to npx with explicit cwd (#1120)
- Remove @chroma-core/default-embed client-side dependency; let Chroma
  HTTP server handle embeddings server-side (#1104, #1105, #1110)

Closes #1010, #1089, #1090, #1068, #1120, #1104, #1105, #1110

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

src/services/worker/SDKAgent.ts

@@ -272,6 +272,12 @@ export class SDKAgent {
       }
     }
 
+    // Ensure subprocess is terminated after query completes
+    const tracked = getProcessBySession(session.sessionDbId);
+    if (tracked && !tracked.process.killed && tracked.process.exitCode === null) {
+      await ensureProcessExit(tracked, 5000);
+    }
+
     // Mark session complete
     const sessionDuration = Date.now() - session.startTime;
     logger.success('SDK', 'Agent completed', {