fix(ios): break audio session route-change feedback loop

handleRouteChange called applyConfiguration() unconditionally, which called
setCategory/setPreferredInput/etc., which triggered another route-change
notification, which called applyConfiguration() again — an infinite loop that
burned CPU (phone slowdown) and repeatedly tore down/rebuilt the audio session
(audio cycling on/off, VoiceOver glitching).

Two fixes:
1. handleRouteChange now only re-applies config on external device changes
   (.oldDeviceUnavailable / .newDeviceAvailable), not on .categoryChange /
   .routeConfigurationChange which are triggered by our own setCategory calls.
2. IOSAudioRouter.applyConfiguration() gained a re-entrancy guard
   (isApplyingConfiguration) for synchronous route-change notifications.

Also added os.Logger logging to both files (subsystem cat.voice.VoiceCatiOS)
so future issues can be debugged from Console.app on the Mac.

clients/apple/iOS/VoiceCatiOS/AudioSessionManager.swift

@@ -1,6 +1,9 @@
 import AVFoundation
+import os
 import VoiceCatCore
 
+private let logger = Logger(subsystem: "cat.voice.VoiceCatiOS", category: "AudioSessionManager")
+
 @MainActor
 final class AudioSessionManager {
     static let shared = AudioSessionManager()
@@ -57,12 +60,47 @@ final class AudioSessionManager {
     }
 
     @objc private func handleRouteChange(_ notification: Notification) {
-        // Refresh the router's published state so the Settings UI updates, and re-apply
-        // the stored preferences (the new route may need the preferred input re-set).
+        guard let info = notification.userInfo,
+              let reasonValue = info[AVAudioSessionRouteChangeReasonKey] as? UInt,
+              let reason = AVAudioSession.RouteChangeReason(rawValue: reasonValue)
+        else {
+            logger.warning("routeChange — unknown reason, refreshing only")
+            IOSAudioRouter.shared.refreshRoutes()
+            NotificationCenter.default.post(name: .voiceCatDeviceListChanged, object: nil)
+            return
+        }
+
+        logger.info("routeChange reason=\(self.reasonLabel(reason))")
+
+        // Re-apply preferences ONLY on external device plug/unplug. Do NOT re-apply on
+        // .categoryChange / .routeConfigurationChange — those are triggered by our own
+        // applyConfiguration() calls (setCategory, setPreferredInput, etc.), and re-applying
+        // would create an infinite notification loop:
+        //   handleRouteChange → applyConfiguration → setCategory → routeChange → ...
+        // That loop burns CPU and cycles the audio session on/off — the "glitching" bug.
+        // IOSAudioRouter.applyConfiguration() also has a re-entrancy guard for synchronous
+        // notifications, but the reason check here is the primary defense.
+        if reason == .oldDeviceUnavailable || reason == .newDeviceAvailable {
+            logger.info("routeChange — external device change, re-applying config")
+            IOSAudioRouter.shared.applyConfiguration()
+        }
+
         IOSAudioRouter.shared.refreshRoutes()
-        IOSAudioRouter.shared.applyConfiguration()
         NotificationCenter.default.post(name: .voiceCatDeviceListChanged, object: nil)
     }
+
+    private func reasonLabel(_ reason: AVAudioSession.RouteChangeReason) -> String {
+        switch reason {
+        case .oldDeviceUnavailable: return "oldDeviceUnavailable"
+        case .newDeviceAvailable: return "newDeviceAvailable"
+        case .categoryChange: return "categoryChange"
+        case .override: return "override"
+        case .wakeFromSleep: return "wakeFromSleep"
+        case .noSuitableRouteForCategory: return "noSuitableRouteForCategory"
+        case .routeConfigurationChange: return "routeConfigurationChange"
+        @unknown default: return "unknown"
+        }
+    }
 }
 
 extension Notification.Name {