Voice: harden startEngine against "Could not start recording"

Addresses the most common causes of the engine failing to start:
- Defensive teardown before starting (removeTap + stop + reset) — a leftover tap
  from a prior attempt makes installTap throw "already has a tap".
- Validate the input node's hardware format (sampleRate/channels > 0) and fail
  with a clear "No microphone input" message instead of throwing.
- Use inputNode.inputFormat(forBus:0) for the tap.
- Category .playAndRecord + [.duckOthers, .defaultToSpeaker] (more permissive
  than .record with .duckOthers).
- Surface the underlying NSError domain+code in the banner + log to pinpoint any
  remaining device-specific failure.

DEBUG-only KISANI_VOICE_START hook to drive the real engine on a sim.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

KisaniCal/Managers/SpeechRecognizer.swift

@@ -61,9 +61,15 @@ final class SpeechRecognizer: ObservableObject {
     }
 
     private func startEngine() {
+        // Defensive teardown: a tap left over from a previous (failed) attempt makes
+        // installTap throw "already has a tap" → "Could not start recording".
+        audioEngine.inputNode.removeTap(onBus: 0)
+        if audioEngine.isRunning { audioEngine.stop() }
+        audioEngine.reset()
+
         do {
             let session = AVAudioSession.sharedInstance()
-            try session.setCategory(.record, mode: .measurement, options: .duckOthers)
+            try session.setCategory(.playAndRecord, mode: .measurement, options: [.duckOthers, .defaultToSpeaker])
             try session.setActive(true, options: .notifyOthersOnDeactivation)
 
             guard let recognizer, recognizer.isAvailable else {
@@ -72,6 +78,17 @@ final class SpeechRecognizer: ObservableObject {
                 return
             }
 
+            // Use the input node's actual hardware format. A 0-sample-rate format
+            // (no usable input — e.g. a simulator with no audio input) would make
+            // installTap throw, so fail with a clear message instead.
+            let node = audioEngine.inputNode
+            let fmt  = node.inputFormat(forBus: 0)
+            guard fmt.sampleRate > 0, fmt.channelCount > 0 else {
+                error = "No microphone input available on this device."
+                print("[VOICE] Invalid input format: \(fmt)")
+                return
+            }
+
             let req = SFSpeechAudioBufferRecognitionRequest()
             req.shouldReportPartialResults = true
             self.request = req
@@ -97,8 +114,6 @@ final class SpeechRecognizer: ObservableObject {
                 }
             }
 
-            let node = audioEngine.inputNode
-            let fmt  = node.outputFormat(forBus: 0)
             node.installTap(onBus: 0, bufferSize: 1024, format: fmt) { [weak self] buf, _ in
                 self?.request?.append(buf)
             }
@@ -109,8 +124,9 @@ final class SpeechRecognizer: ObservableObject {
             print("[VOICE] Recording started")
 
         } catch {
-            self.error = "Could not start recording."
-            print("[VOICE] Engine start failed: \(error)")
+            let ns = error as NSError
+            self.error = "Could not start recording. (\(ns.domain) \(ns.code))"
+            print("[VOICE] Engine start failed: \(ns.domain) \(ns.code) — \(error.localizedDescription)")
             stopEngine()
         }
     }

KisaniCal/Views/TodayView.swift

@@ -1879,6 +1879,9 @@ struct AddTaskSheet: View {
                 if let t = ProcessInfo.processInfo.environment["KISANI_VOICE_SIM"], !t.isEmpty {
                     DispatchQueue.main.asyncAfter(deadline: .now() + 0.6) { speech.transcript = t }
                 }
+                if ProcessInfo.processInfo.environment["KISANI_VOICE_START"] == "1" {
+                    DispatchQueue.main.asyncAfter(deadline: .now() + 0.6) { speech.start() }
+                }
             }
             #endif
             .padding(.horizontal, 16)