Add macOS ARM64 Desktop lab lane

[lefoulkrod]

What changed

• add an exact-DMG macOS ARM64 hardware smoke and full Accessibility-driven Desktop lane
• add a focused --only boundaries mode for fast native-host iteration before full-suite execution
• exercise first run, returning launch, Doctor recovery, interrupted resume, candidate update reconciliation, occupied-port recovery, and a real Custom App WebView action
• automate native agent export and Finder import, artifact preview/download, completion toasts, Command-plus zoom, and visible updater skip/state behavior
• add a trusted coordinate-input path for native and WebKit elements that expose no AXPress, without adding a production WebDriver or test-only application bridge
• keep test apps, configuration, containers, volumes, and downloads namespaced and disposable while preserving personal installs
• document the macOS lane and its remaining manual boundaries

Why

Linux and Windows Desktop releases already have automated package and UI lanes, but Apple Silicon required native macOS behavior that cannot be represented faithfully in a Linux container. The physical-host backend in omnideck-dev/vm-lab#2 makes this possible on a constrained M1 Air while keeping builds off-host.

Impact

Release qualification can now exercise the production ARM64 DMG and native Desktop behavior on real Apple Silicon. The fast boundary mode supports short debugging loops; the full mode remains the release-grade 14-journey lane.

Validation

• rebased onto current origin/main
• shell syntax checks for all added macOS scripts
• 46 JavaScript source/contract tests passed
• 17 Python WebDriver/host-boundary tests passed
• focused native-boundary lane passed: /mnt/data/VMs/omnideck-release-lab/artifacts/desktop/macos-e2e/20260814T022917Z-3652969
• full Desktop lane passed: /mnt/data/VMs/omnideck-release-lab/artifacts/desktop/macos-e2e/20260814T023425Z-3669420
• canonical CLI/TUI + Desktop aggregate passed: /mnt/data/VMs/omnideck-release-lab/artifacts/macos/aggregate/20260814T023256Z-3665073

Dependencies

• consumes the physical-host/bootstrap support in Add native macOS ARM64 lab lane vm-lab#2
• validated together with the CLI consumer in Add macOS ARM64 CLI lab lane cli#60