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>

package.json

@@ -97,7 +97,6 @@
   },
   "dependencies": {
     "@anthropic-ai/claude-agent-sdk": "^0.1.76",
-    "@chroma-core/default-embed": "^0.1.9",
     "@modelcontextprotocol/sdk": "^1.25.1",
     "ansi-to-html": "^0.7.2",
     "chromadb": "^3.2.2",