[gyng]

Queued desktop-layer placement could outlive a layer change or destroyed overlay, and a delayed frontend enable could overwrite a newer layer selection. Run native placement on the UI thread against current registrations and desktop state, coalesce pending work, serialize presentation changes, distinguish each instance's sentinel, pause inactive polling, and avoid registration on watcher startup failure.

Credit Kjell Naessens (@naessenskjell) for PR #78 in README Contributors and the v0.0.71 release notes. Document the native smoke test and the requested PR-review/release workflow in AGENTS.md.

Validation:

• 4,698 frontend tests; 100% coverage in all metrics.
• 126 Playwright tests, including desktop-layer opt-in persistence.
• 451 Rust tests passed; 6 intentionally ignored in the ordinary suite.
• Typecheck, zero-warning frontend lint, production build, rustfmt, and clippy passed.
• Explicit native Win+D smoke passed on Windows 11 25H2 build 26200.9445 with three connected monitors: visibility above desktop icons, native input hit testing, return from Show Desktop, and another sentinel with the same class.

The native smoke uses temporary Win32 windows, rather than real WebView widget interactions. Older Windows shell versions were not tested. No known medium-or-higher issues remain from this review.