feat: 快速双击 Fn 键切换语音输入/AI 助手模式

Sources/App/AppDelegate.swift

@@ -80,6 +80,18 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
         keyMonitor.onFnUp = { [weak self] in
             self?.stopRecording()
         }
+        keyMonitor.onFnDoubleClick = { [weak self] in
+            self?.toggleModeViaDoubleClick()
+        }
+    }
+
+    // MARK: - Double-Click Mode Switch
+
+    private func toggleModeViaDoubleClick() {
+        let newMode: TriggerMode = Config.shared.triggerMode == .input ? .assist : .input
+        Config.shared.triggerMode = newMode
+        menuBarController.refreshModeMenu()
+        print("[App] Double-click: mode switched to \(newMode)")
     }
 
     // MARK: - Recording

Sources/App/MenuBarController.swift

@@ -201,6 +201,10 @@ final class MenuBarController: NSObject {
         return true
     }
 
+    func refreshModeMenu() {
+        updateModeMenuState()
+    }
+
     private func updateInputLLMMenuState() {
         inputLLMEnabledItem.state = Config.shared.inputLLM.enabled ? .on : .off
     }

Sources/Core/KeyMonitor.swift

@@ -1,18 +1,28 @@
 import Cocoa
 import CoreGraphics
 
-/// 全局热键监听器：只监听 Fn 键
+/// 全局热键监听器：只监听 Fn 键（支持双击切换模式）
 final class KeyMonitor {
 
     // Fn 键标志
     private static let fnMask: UInt64 = 0x00800000
 
+    // 双击检测
+    private static let doubleClickWindow: TimeInterval = 0.40   // 两次点击的最大间隔
+    private static let longPressThreshold: TimeInterval = 0.20  // 长按判定阈值
+
     private var eventTap: CFMachPort?
     private var runLoopSource: CFRunLoopSource?
     private var isFnPressed = false
 
+    // 时间戳追踪
+    private var lastFnUpTime: TimeInterval = 0
+    private var fnDownTime: TimeInterval = 0
+    private var longPressTimer: Timer?
+
     var onFnDown: (() -> Void)?
     var onFnUp: (() -> Void)?
+    var onFnDoubleClick: (() -> Void)?    // 双击 Fn 切换模式
 
     func start() -> Bool {
         guard eventTap == nil else { return true }
@@ -86,17 +96,51 @@ final class KeyMonitor {
 
         if fnActive && !isFnPressed {
             isFnPressed = true
-            print("[KeyMonitor] ⚡️ Fn DOWN")
-            DispatchQueue.main.async { [weak self] in
-                self?.onFnDown?()
+            fnDownTime = ProcessInfo.processInfo.systemUptime
+
+            // 检测双击：上次松开距现在 < 400ms 且之前有单击
+            let elapsed = fnDownTime - lastFnUpTime
+            if elapsed > 0 && elapsed < Self.doubleClickWindow {
+                // 双击！切换模式，取消长按 timer
+                longPressTimer?.invalidate()
+                longPressTimer = nil
+                print("[KeyMonitor] ⚡️ Fn DOUBLE-CLICK → switch mode")
+                DispatchQueue.main.async { [weak self] in
+                    self?.onFnDoubleClick?()
+                }
+                return nil
+            }
+
+            // 延迟 200ms 判定是否为长按
+            print("[KeyMonitor] ⚡️ Fn DOWN (waiting for long-press/double-click)")
+            longPressTimer?.invalidate()
+            longPressTimer = Timer.scheduledTimer(withTimeInterval: Self.longPressThreshold, repeats: false) { [weak self] _ in
+                guard let self = self, self.isFnPressed else { return }
+                print("[KeyMonitor] ⚡️ Fn LONG-PRESS → start recording")
+                self.longPressTimer = nil
+                DispatchQueue.main.async {
+                    self.onFnDown?()
+                }
             }
             return nil
         }
         if !fnActive && isFnPressed {
             isFnPressed = false
-            print("[KeyMonitor] ⚡️ Fn UP")
-            DispatchQueue.main.async { [weak self] in
-                self?.onFnUp?()
+            lastFnUpTime = ProcessInfo.processInfo.systemUptime
+
+            // 取消长按 timer（说明是短按/单击）
+            longPressTimer?.invalidate()
+            longPressTimer = nil
+
+            print("[KeyMonitor] ⚡️ Fn UP (was pressed for \(String(format: "%.0f", (lastFnUpTime - fnDownTime) * 1000))ms)")
+
+            // 如果长按 timer 已被触发（已开始录音），正常触发 onFnUp
+            // 否则这是短按（单击或双击的第一下），不触发录音
+            if lastFnUpTime - fnDownTime >= Self.longPressThreshold {
+                // 长按结束，正常触发 onFnUp
+                DispatchQueue.main.async { [weak self] in
+                    self?.onFnUp?()
+                }
             }
             return nil
         }