feat(bar): notch bar appearance option (LAC-3037)

[lacymorrow]

Summary

Implements the notch bar appearance from the LAC-3030 investigation (plan: docs/plans/notch-bar-appearance-option.md). Paperclip issue: LAC-3037.

The floating bar can now dock top-flush over the MacBook notch, above the menu bar — a Dynamic-Island-style home for Juno's status/input UI.

Backend (Rust)

• notch_layout module (platform/macos.rs) — pure, platform-independent layout math: notch geometry from safeAreaInsets / auxiliaryTopLeftArea/auxiliaryTopRightArea, fixed canvas sizing, top-flush centered frame. 6 unit tests.
• notch module — enter_notch_mode / exit_notch_mode on the main thread via run_on_main_thread round-trips; window level NSMainMenuWindowLevel+3 (27); overlay collection behavior re-asserted on every mode entry (macOS silently drops CanJoinAllSpaces on re-order). Non-macOS stubs keep the option selectable elsewhere.
• get_notch_geometry command — frontend reads the silhouette dimensions from the backend (single source of truth).
• Persisted appearance is re-applied at startup; switching away restores the default floating frame and NSFloatingWindowLevel.

Frontend (TS)

• NotchBar component — black silhouette welded to the bezel. All state transitions (idle → hover peek → input → working/listening/error) are CSS-only inside a fixed window canvas; the window is never resized per state, so the shape never detaches from the bezel mid-animation.
• No drag/resize hooks in notch mode — placement is backend-computed.
• Notch-less Macs / external displays get a centered pill fallback inside the menu bar.
• Settings: “Notch (Menu Bar)” option in General → bar appearance.

Out of scope (per plan, file separately)

Non-activating-panel typing, click-through cursor poll, SkyLight space pinning.

Verification

• cargo check clean; cargo clippy 0 warnings
• cargo test notch_layout: 6/6 pass
• npx tsc --noEmit clean
• npm test notch-bar.test.tsx: 5/5 pass (silhouette sizing, pill fallback, CSS expansion, input submit, idle click)
• constants.generated.ts regenerated via scripts/generate-ts-constants.js — reproduces the committed diff exactly

⚠️ Still needs a built-app run on notch + notch-less hardware (window level/permission behavior differs from dev builds) — noted in LAC-3037.

Prototype finding

A plain borderless NSWindow at level 27 positioned programmatically is not clamped by constrainFrameRect:toScreen:, so no tauri-nspanel dependency or dynamic ObjC subclass was needed for Phase 1.

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

[lacymorrow]

Review + hardening pass (6f66368). The red `claude-review` check is infrastructure, not a review verdict — the workflow's `CLAUDE_CODE_OAUTH_TOKEN` secret doesn't exist yet (tracked as LAC-3035), so the action fails env validation on every PR. As a substitute, a local code-reviewer agent pass ran over the full diff; fixes applied:

• `enter`/`exit_notch_mode` now return `Result` and failures propagate to the `ui_set_bar_config` caller instead of being logged and swallowed
• The notch bar re-anchors on floating-bar `Moved`/`ScaleFactorChanged` run events (display plug/unplug, scaling changes previously left it stale until the appearance was re-toggled); loop-safe via a `frame_matches` guard that skips `setFrame` when already in place
• Appearance transitions are serialized with a static mutex so overlapping `ui_set_bar_config` calls can't leave the window contradicting the stored config

Verified: `cargo clippy` clean, 7/7 `notch_layout` unit tests pass (incl. new `frame_matches` test), frontend typecheck/build green in CI.