feat(macos): add native menu bar app with notch overlay

Introduces a SwiftUI companion app for the Fail Well PWA: menu bar
status item, popover with task list / record / history views, command
palette, and a Dynamic Island-style notch overlay that shows the active
step and timer beside the hardware notch and expands on hover to reveal
pause/next controls.

macos/README.md

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+# Fail Well — macOS
+
+Menu bar + notch companion to the [Fail Well PWA](../). See [`see-this-pwa-and-proud-porcupine.md`](../../.claude/plans/see-this-pwa-and-proud-porcupine.md) for the design plan.
+
+## Requirements
+
+- macOS 15 Sequoia or later
+- Xcode 16 / Swift 6.0+ toolchain (`xcode-select --install` is enough — full Xcode not required)
+
+## Build & run
+
+```sh
+make run      # release build, packaged into FailWell.app, opened
+make debug    # debug build, packaged and opened
+make test     # swift test
+make clean    # remove .build and FailWell.app
+```
+
+The resulting `FailWell.app` lives next to the `Makefile`. It's an unsigned ad-hoc-signed bundle, fine for local use; for distribution you'd need a Developer ID.
+
+## Layout
+
+```
+macos/
+├── Package.swift
+├── Info.plist                    bundle config (LSUIElement = true → no Dock icon)
+├── Makefile                      build/run/test/package targets
+└── Sources/FailWell/
+    ├── FailWellApp.swift         @main + MenuBarExtra
+    ├── Models/                   Codable Task / Step / TaskRecord / TimeRange
+    ├── Services/                 Parser, BreakCalculator, Comparator, Clock, Storage, Clipboard
+    └── Views/                    SwiftUI popover, command palette, notch overlay
+```
+
+## Data location
+
+`~/Library/Application Support/FailWell/data.json` — versioned, atomic writes.