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/Sources/FailWell/Services/TimeFormat.swift

@@ -0,0 +1,28 @@
+import Foundation
+
+enum TimeFormat {
+    /// "MM:SS" or "H:MM:SS" depending on magnitude.
+    static func clock(_ seconds: TimeInterval) -> String {
+        let total = max(0, Int(seconds))
+        let h = total / 3600
+        let m = (total % 3600) / 60
+        let s = total % 60
+        if h > 0 { return String(format: "%d:%02d:%02d", h, m, s) }
+        return String(format: "%d:%02d", m, s)
+    }
+
+    /// Rounded to minutes. Returns "0m" for sub-minute durations.
+    static func minutes(_ seconds: TimeInterval) -> String {
+        "\(Int((seconds / 60).rounded()))m"
+    }
+
+    /// Compact relative-date string, e.g. "today", "yesterday", "Mar 14".
+    static func date(_ date: Date, relativeTo reference: Date = Date()) -> String {
+        let cal = Calendar.current
+        if cal.isDateInToday(date) { return "today" }
+        if cal.isDateInYesterday(date) { return "yesterday" }
+        let f = DateFormatter()
+        f.dateFormat = cal.component(.year, from: date) == cal.component(.year, from: reference) ? "MMM d" : "MMM d yyyy"
+        return f.string(from: date)
+    }
+}