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. Note the name collision with FlowDeck's own "macOS development" guide (`resources/macos-development.md` in the `flowdeck` skill): that one is about *driving* a running macOS app (clicks, keystrokes, accessibility automation — see `flowdeck ui mac`), not the platform APIs a macOS app is built from. Same name, different subject — for build/run/UI-automation tasks use `flowdeck` directly rather than this skill. ## 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) o