perf(system): gate auto-quit AppleScript probes

[JustYannicc]

Summary

• Gate auto-quit AppleScript probes behind due-candidate checks.
• Cache tracked bundle IDs and tracked music bundle IDs so each poll can prune and decide probe needs without rebuilding sets.
• Add focused auto-quit instrumentation/tests for no-due, due, frontmost, recording, and music gating behavior.

Metrics

• Before: no tracked app due over 3 ticks = 9 osascript calls (frontmost 3, recording 3, music 3, quit 0).
• After: no tracked app due over 3 ticks = 0 osascript calls.
• Before: one non-music app due = 4 osascript calls (frontmost 1, recording 1, music 1, quit 1).
• After: one non-music app due = 3 osascript calls (frontmost 1, recording 1, music 0, quit 1).

Validation

• node scripts/test-auto-quit-manager.mjs
• node scripts/test-auto-quit-manager.mjs --metrics
• node --test scripts/test-*.mjs
• pnpm run build:main
• Codex LSP diagnostics on src/main/auto-quit-manager.ts: no diagnostics found

Risks

• The manager now samples the frontmost app only once at least one tracked app reaches its due time. This is the intended probe reduction, but it means short foreground activations between due checks are not observed until a due candidate exists.

[JustYannicc]

Superseded by consolidated upstream PR #534 (perf(mac): reduce native polling and async IO stalls), which carries this change together with the related macOS/native/audio/camera async IO performance fixes. Closing this source PR so review can continue on #534.