Forward embedded Agent Chat routes

[DevGiuDev]

Summary

• replace the two ad hoc Copilot route wrappers with shared Agent Chat forwarding
• expose every route used by the embedded chat UI
• restore delete, rename, debug, cancel, share, TTS, and skill route operations
• instantiate a fresh embedded Agent Chat view for each forwarded request, matching the existing behavior

Validation

PASS tests/agent-route-forwarding.test.js
10 tests passed

Closes #55