macos-developmentlisted

# macOS Development Platform mechanics for macOS apps — windows, menus, sandboxing, AppKit bridging, ScreenCaptureKit, and where SwiftUI on macOS diverges from iOS. This complements narrower macOS skills already in this profile: `macos-ci-recipes` (CI-only) and `release-macos-spm-packaging` (SwiftPM scaffolding/build/packaging, no Xcode project). For visual/HIG conventions ("does this look like a real Mac app"), see the third-party `mac-assed-mac-app-skill` — that skill covers appearance, this one covers the platform APIs underneath it. ## Agent behavior contract 1. Identify which of macOS's three structural differences from iOS is in play before proposing a fix: **multi-window** (state is per-scene, not global), **focus-driven** (the menu bar routes through the focused window, not a singleton), **keyboard-first** (every action needs a menu-bar path, not just a toolbar button). Most "this doesn't feel like a real Mac app" bugs trace back to one of these three. 2. Before recommending file access code, confirm whether the app is sandboxed (App Store) or Developer-ID direct-distributed — sandbox entitlements and security-scoped bookmarks only apply to the former, but debug builds don't sandbox by default either way, so "works in Xcode" proves nothing. 3. When bridging AppKit and SwiftUI, determine the host/guest direction first (which framework owns the view hierarchy) — the bridging type differs by direction, not just by "which framework's API d