wz-phone/docs/PRD-desktop-direct-calling.md

PRD: Desktop Direct Calling — Backport SignalManager

Problem

The desktop Tauri app has the direct calling UI (Room/Direct Call toggle, Register, Call buttons) but the backend uses inline async code in main.rs instead of a proper SignalManager. This needs to be backported from the Android refactor.

Tasks

1. Create signal_mgr.rs for desktop — same pattern as Android, or reuse the crate directly
2. Wire into Tauri commands — register_signal should use SignalManager::connect() + run_recv_loop() on a dedicated thread
3. State polling — get_signal_status should call SignalManager::get_state_json()
4. place_call / answer_call — delegate to SignalManager methods
5. Merge android branch into desktop branch — resolve the 37 desktop-only + 90 android-only commit divergence
6. Test — Android calls Desktop, Desktop calls Android

UI Fixes

1. Default alias — generate random name on first start (like Android does)
2. Default room — change from "android" to "general"
3. Fingerprint display — ensure full xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx format (not truncated)
4. Deregister button — ability to disconnect signal channel
5. Call state reset — after hangup, return to "Registered" state, not stuck on "Ringing"