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/BreakCalculator.swift

@@ -0,0 +1,22 @@
+import Foundation
+
+enum BreakCalculator {
+    /// Shifts the `start` of any unfinished step records forward by the break duration.
+    /// Mirrors `addBreakTimeToStepRecords` from the PWA.
+    static func applyingBreakTime(to record: TaskRecord) -> TaskRecord {
+        guard let breakTime = record.breakTime, let breakEnd = breakTime.end else {
+            return record
+        }
+
+        let diff = breakEnd.timeIntervalSince(breakTime.start)
+
+        var updated = record
+        for (stepId, range) in updated.stepRecords where range.end == nil {
+            updated.stepRecords[stepId] = TimeRange(
+                start: range.start.addingTimeInterval(diff),
+                end: nil
+            )
+        }
+        return updated
+    }
+}