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>

FocusFixer/FocusEnforcer.swift

@@ -0,0 +1,60 @@
+import AppKit
+import ApplicationServices
+import os
+
+/// Activates the app that owns a window and reasserts keyboard focus on
+/// that specific window via the Accessibility API.
+final class FocusEnforcer {
+    private let logger = Logger(subsystem: "com.local.focusfixer", category: "FocusEnforcer")
+    private let preferences: Preferences
+
+    init(preferences: Preferences = .shared) {
+        self.preferences = preferences
+    }
+
+    /// Activates the owning app and raises/focuses its window, unless it is
+    /// this app, already frontmost, or user-excluded.
+    func enforceFocus(forWindowOwnedBy pid: pid_t) {
+        guard pid != ProcessInfo.processInfo.processIdentifier else {
+            return
+        }
+        guard let app = NSRunningApplication(processIdentifier: pid) else {
+            logger.debug("No running application for pid \(pid, privacy: .public)")
+            return
+        }
+        if let bundleID = app.bundleIdentifier, preferences.isExcluded(bundleID: bundleID) {
+            return
+        }
+        guard !app.isActive else {
+            return
+        }
+
+        if !app.activate(options: []) {
+            logger.debug("Activation returned false for pid \(pid, privacy: .public)")
+        }
+        raiseFocusedWindow(pid: pid)
+    }
+
+    private func raiseFocusedWindow(pid: pid_t) {
+        let axApp = AXUIElementCreateApplication(pid)
+        var windowRef: CFTypeRef?
+        let copyResult = AXUIElementCopyAttributeValue(axApp, kAXFocusedWindowAttribute as CFString, &windowRef)
+        guard copyResult == .success, let windowRef else {
+            logger.debug("Could not resolve focused window via AX for pid \(pid, privacy: .public): \(copyResult.rawValue, privacy: .public)")
+            return
+        }
+        // AXUIElementCopyAttributeValue guarantees an AXUIElement on success; the
+        // Swift compiler can't express that constraint, hence the forced cast.
+        let axWindow = windowRef as! AXUIElement
+
+        let raiseResult = AXUIElementPerformAction(axWindow, kAXRaiseAction as CFString)
+        if raiseResult != .success {
+            logger.debug("Raise action failed for pid \(pid, privacy: .public): \(raiseResult.rawValue, privacy: .public)")
+        }
+
+        let focusResult = AXUIElementSetAttributeValue(axApp, kAXFocusedWindowAttribute as CFString, axWindow)
+        if focusResult != .success {
+            logger.debug("Setting focused window failed for pid \(pid, privacy: .public): \(focusResult.rawValue, privacy: .public)")
+        }
+    }
+}