fix(voice): keep clicked calls bound to their chat

[johnmatthewtennant]

Summary

Keeps Voice Conversation bound to the chat and window that initiated it without relying on transient focus.

• Authorizes starts against the foreground session generation and window ownership.
• Allows focus to move to voice controls without rejecting the clicked call.
• Rejects stale starts after a different window or session replaces the foreground target.

Reviewer example

Click the call control in a chat, then let focus move to the voice controls while startup is in flight. The call remains attached to that chat; a stale start from another foreground generation is rejected.

Testing

• just check
• just tauri-check
• just clippy

[morgmart]

🤖 Automated code review

APPROVE. Fresh static review of the exact three-dot comparison 1366fb9...7dac06f found no publishable findings. The change removes window-focus as an authorization proxy while retaining renderer epoch, foreground-session generation, stable session ownership, and serialized lifecycle validation. The replacement-stop and voice-start paths were traced through validation and lifecycle boundaries; the changed unit test discriminates ownership acceptance and rejection. Final self-check covered the changed voice start/replacement flows, accessibility, localization, navigation/consent guards, async/error/never-completes/lifecycle/race behavior, test honesty, project laws and design-system rules, duplicate overlap, and blocking-evidence quality. This backend-only change introduces no visual, accessibility, or localization surface. Supplied GitHub evidence was inspected: all nine check runs for the exact head SHA completed successfully, while the legacy combined commit status is pending with no contexts; required checks still independently govern merge readiness.

Deterministic publication result: 0 blocking and 0 non-blocking finding(s) publishable; 0 duplicate(s) suppressed.

Pending checks: 1 check(s) are not complete.

This approval reflects the completed code review only; merge readiness remains governed by the repository's required checks.