Initial FocusFixer implementation

Menu-bar utility that fixes cross-display keyboard focus loss: a
listen-only CGEvent tap locates the window under the cursor and
reasserts app activation + AX focus on it, with debounce, tap
auto-recovery, and an Accessibility permission gate.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

FocusFixerTests/DebounceTests.swift

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+import XCTest
+@testable import FocusFixer
+
+final class DebounceTests: XCTestCase {
+    func testFirstEventIsAlwaysProcessed() {
+        var clockValue: TimeInterval = 0
+        var debouncer = Debouncer(interval: 0.15, clock: { clockValue })
+        XCTAssertTrue(debouncer.shouldProcess())
+    }
+
+    func testEventWithinIntervalIsSuppressed() {
+        var clockValue: TimeInterval = 0
+        var debouncer = Debouncer(interval: 0.15, clock: { clockValue })
+        XCTAssertTrue(debouncer.shouldProcess())
+
+        clockValue += 0.05
+        XCTAssertFalse(debouncer.shouldProcess())
+    }
+
+    func testEventAfterIntervalIsProcessed() {
+        var clockValue: TimeInterval = 0
+        var debouncer = Debouncer(interval: 0.15, clock: { clockValue })
+        XCTAssertTrue(debouncer.shouldProcess())
+
+        clockValue += 0.2
+        XCTAssertTrue(debouncer.shouldProcess())
+    }
+
+    func testAcceptedEventResetsTheWindow() {
+        var clockValue: TimeInterval = 0
+        var debouncer = Debouncer(interval: 0.15, clock: { clockValue })
+        XCTAssertTrue(debouncer.shouldProcess())
+
+        clockValue += 0.2
+        XCTAssertTrue(debouncer.shouldProcess())
+
+        clockValue += 0.05
+        XCTAssertFalse(debouncer.shouldProcess())
+    }
+}

FocusFixerTests/PreferencesTests.swift

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+import XCTest
+@testable import FocusFixer
+
+final class PreferencesTests: XCTestCase {
+    private var suiteName: String!
+    private var defaults: UserDefaults!
+    private var preferences: Preferences!
+
+    override func setUp() {
+        super.setUp()
+        suiteName = "com.local.focusfixer.tests.\(UUID().uuidString)"
+        defaults = UserDefaults(suiteName: suiteName)
+        preferences = Preferences(defaults: defaults)
+    }
+
+    override func tearDown() {
+        defaults.removePersistentDomain(forName: suiteName)
+        preferences = nil
+        defaults = nil
+        suiteName = nil
+        super.tearDown()
+    }
+
+    func testDefaultsToEnabled() {
+        XCTAssertTrue(preferences.isEnabled)
+    }
+
+    func testDefaultDebounceIntervalIs150ms() {
+        XCTAssertEqual(preferences.debounceInterval, 0.15, accuracy: 0.0001)
+    }
+
+    func testExclusionListMatching() {
+        XCTAssertFalse(preferences.isExcluded(bundleID: "com.apple.finder"))
+
+        preferences.setExcluded(true, bundleID: "com.apple.finder")
+        XCTAssertTrue(preferences.isExcluded(bundleID: "com.apple.finder"))
+
+        preferences.setExcluded(false, bundleID: "com.apple.finder")
+        XCTAssertFalse(preferences.isExcluded(bundleID: "com.apple.finder"))
+    }
+
+    func testExclusionListRequiresExactMatch() {
+        preferences.setExcluded(true, bundleID: "com.local.focusfixer.helper")
+        XCTAssertFalse(preferences.isExcluded(bundleID: "com.local.focusfixer"))
+        XCTAssertTrue(preferences.isExcluded(bundleID: "com.local.focusfixer.helper"))
+    }
+}

FocusFixerTests/WindowLocatorTests.swift

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+import XCTest
+@testable import FocusFixer
+
+final class WindowLocatorTests: XCTestCase {
+    func testReturnsOwnerPIDWhenPointInsideWindow() {
+        let windows = [
+            WindowInfo(ownerPID: 111, layer: 0, bounds: CGRect(x: 0, y: 0, width: 100, height: 100))
+        ]
+        XCTAssertEqual(WindowLocator.ownerPID(at: CGPoint(x: 50, y: 50), in: windows), 111)
+    }
+
+    func testIgnoresNonZeroLayerWindows() {
+        let windows = [
+            WindowInfo(ownerPID: 999, layer: 25, bounds: CGRect(x: 0, y: 0, width: 100, height: 100))
+        ]
+        XCTAssertNil(WindowLocator.ownerPID(at: CGPoint(x: 50, y: 50), in: windows))
+    }
+
+    func testFallsThroughToNextWindowWhenTopWindowIsWrongLayer() {
+        let windows = [
+            WindowInfo(ownerPID: 1, layer: 25, bounds: CGRect(x: 0, y: 0, width: 100, height: 100)),
+            WindowInfo(ownerPID: 2, layer: 0, bounds: CGRect(x: 0, y: 0, width: 100, height: 100))
+        ]
+        XCTAssertEqual(WindowLocator.ownerPID(at: CGPoint(x: 50, y: 50), in: windows), 2)
+    }
+
+    func testReturnsFrontmostWindowInZOrder() {
+        // Overlapping layer-0 windows: front-to-back order (as returned by
+        // CGWindowListCopyWindowInfo) determines which owner wins.
+        let windows = [
+            WindowInfo(ownerPID: 1, layer: 0, bounds: CGRect(x: 0, y: 0, width: 200, height: 200)),
+            WindowInfo(ownerPID: 2, layer: 0, bounds: CGRect(x: 0, y: 0, width: 200, height: 200))
+        ]
+        XCTAssertEqual(WindowLocator.ownerPID(at: CGPoint(x: 50, y: 50), in: windows), 1)
+    }
+
+    func testEmptyWindowListReturnsNil() {
+        XCTAssertNil(WindowLocator.ownerPID(at: CGPoint(x: 50, y: 50), in: []))
+    }
+
+    func testPointOutsideAllWindowsReturnsNil() {
+        let windows = [
+            WindowInfo(ownerPID: 1, layer: 0, bounds: CGRect(x: 0, y: 0, width: 100, height: 100))
+        ]
+        XCTAssertNil(WindowLocator.ownerPID(at: CGPoint(x: 500, y: 500), in: windows))
+    }
+}