fix: auto-end Stay when meeting ends

[avatarneil]

Stay now turns itself off when the protected meeting ends, including native-app paths where Zoom returns to Home or another Zoom shell after the call closes. The classifier is more conservative about native meeting apps: app identity alone is no longer enough when the active window is a known non-meeting shell, while browser meetings still lock on other tabs and end when the protected meeting tab/window stops matching a meeting.

The desktop shell now gets out of the way after PIN setup and other idle-ready transitions, using the macOS app hide/show path so Stay itself does not remain the foreground window and block focus polling. When macOS reports a native app like Zoom with an empty CGWindow title, the platform adapter enriches that snapshot from the focused Accessibility window title before classification; this keeps Zoom Home filtered while allowing a live Zoom Meeting window to prompt correctly. Prompt/lock windows also raise and focus when they need user attention.

Native meeting-app end signals from a different window now require confirmation on consecutive polls. That keeps a transient Zoom shell/window observation during app switching from ending the Stay, while still allowing a repeated Zoom Home/Workplace signal to auto-end after the meeting is actually gone. High-confidence cases where the protected meeting window itself stops matching still end immediately.

This follows the shape used by stronger meeting tools: prefer high-confidence signals such as calendar/video links, live audio/call activity, and explicit supported-app state; when Stay only has foreground app/title/window metadata, treat native app shell titles as low confidence instead of prompting on them, and use platform-specific metadata enrichment where the generic provider is incomplete.

Tested with cargo fmt --all --check, cargo test --workspace, bun run test, and bun run typecheck.

---