Add connection-bound reply handles for app-server requests

[copyberry]

Add connection-bound reply handles for app-server requests

Why

Server request IDs can be reused across connections. Retained replies need to target the connection that emitted the request, even if the UI selection later changes.

What changed

• Expose AppServerReplyHandle through AppServerRequestHandle::server_request_reply_handle, capturing the originating client and request ID for explicit resolve or reject calls.
• Share single-use completion state across clones so only the first reply is submitted. Dropping a handle sends nothing; stale connections return I/O errors without retrying or switching connections.
• Route existing client reply methods through request handles and use the new API in the managed worktree model test.

Testing

Add in-process and WebSocket tests for replies on separate connections with identical request IDs, rejection routing, duplicate completion, and stale handles after worker shutdown. Also check that debug output redacts handle details.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	🔄 Running since 2026-10-11T06:08:52.893233Z	3fd44fa	PR opened

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