feat: voice session hardening - client reconnect and heartbeat

- Client attempts to find existing session by DeviceId before creating new
- Add heartbeat timer (5 min) to keep server session alive during idle periods
- Dispose heartbeat timer on session end
- Add TurnCounter and TranscriptCount to McpVoiceSessionStatus
- Add FindExistingSessionAsync to McpVoiceConversationService

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: sharpninja

lib/McpServer

@@ -83,6 +83,7 @@ public partial class SimplifiedVoiceView : UserControl
     private bool _sendRequested;
     private string? _manualText;
     private bool _foregroundServiceRunning;
+    private Timer? _heartbeatTimer;
     private TextBox? _textInputBox;
     private Button? _pauseButton;
     private Button? _stopButton;
@@ -219,6 +220,9 @@ private async Task StartSessionAsync()
         // Start foreground service to keep voice alive in background
         StartForegroundService("Voice session active. Listening...");
 
+        // Start heartbeat to keep session alive during idle periods
+        _heartbeatTimer = new Timer(OnHeartbeatTick, null, TimeSpan.FromMinutes(5), TimeSpan.FromMinutes(5));
+
         // Announce readiness and start listening
         PlayChime();
 
@@ -234,6 +238,8 @@ private async Task StartSessionAsync()
         }
         finally
         {
+            _heartbeatTimer?.Dispose();
+            _heartbeatTimer = null;
             _conversationActive = false;
             _isPaused = false;
             _isSpeaking = false;
@@ -757,6 +763,25 @@ private void SubmitTypedText()
             _textInputBox.Text = string.Empty;
     }
 
+    private void OnHeartbeatTick(object? state)
+    {
+        var vm = VM;
+        if (vm == null || !_sessionReady || string.IsNullOrWhiteSpace(vm.SessionId)) return;
+
+        _ = Task.Run(async () =>
+        {
+            try
+            {
+                await vm.RefreshStatusCommand.ExecuteAsync(null).ConfigureAwait(false);
+                _logger.LogDebug("Heartbeat OK for session {SessionId}", vm.SessionId);
+            }
+            catch (Exception ex)
+            {
+                _logger.LogWarning(ex, "Heartbeat failed for session {SessionId}", vm.SessionId);
+            }
+        });
+    }
+
     private void UpdateButtons()
     {
         Dispatcher.UIThread.Post(() =>

src/McpServerManager.Android/Views/SimplifiedVoiceView.axaml.cs

@@ -121,6 +121,12 @@ public sealed record McpVoiceSessionStatus
 
     [JsonPropertyName("lastTurnId")]
     public string? LastTurnId { get; init; }
+
+    [JsonPropertyName("turnCounter")]
+    public int TurnCounter { get; init; }
+
+    [JsonPropertyName("transcriptCount")]
+    public int TranscriptCount { get; init; }
 }
 
 /// <summary>Transcript response payload for a voice session.</summary>

src/McpServerManager.Core/Models/McpVoiceConversationContracts.cs

@@ -226,6 +226,22 @@ public async Task<McpVoiceTranscriptResponse> GetTranscriptAsync(string sessionI
             ?? throw new InvalidOperationException("MCP voice transcript returned an empty response.");
     }
 
+    /// <summary>
+    /// Finds an active voice session for the specified device.
+    /// Returns <c>null</c> if no active session exists.
+    /// </summary>
+    public async Task<McpVoiceSessionStatus?> FindExistingSessionAsync(string deviceId, CancellationToken cancellationToken = default)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(deviceId);
+
+        using var client = await CreateAuthorizedClientAsync(TimeSpan.FromSeconds(15), cancellationToken).ConfigureAwait(true);
+        using var response = await client.GetAsync($"mcpserver/voice/session?deviceId={Uri.EscapeDataString(deviceId)}", cancellationToken).ConfigureAwait(true);
+        if (response.StatusCode == HttpStatusCode.NotFound)
+            return null;
+        await EnsureSuccessAsync(response, cancellationToken).ConfigureAwait(true);
+        return await response.Content.ReadFromJsonAsync<McpVoiceSessionStatus>(JsonOptions, cancellationToken).ConfigureAwait(true);
+    }
+
     /// <summary>
     /// Deletes a voice session and any associated in-memory state.
     /// </summary>

src/McpServerManager.Core/Services/McpVoiceConversationService.cs

@@ -91,13 +91,40 @@ private async Task CreateSessionAsync()
         IsBusy = true;
         try
         {
+            var deviceId = Environment.MachineName;
+
+            // Try to reconnect to an existing session for this device
+            GlobalStatusChanged?.Invoke("Looking for existing voice session...");
+            StatusText = "Looking for existing voice session...";
+            try
+            {
+                var existing = await _voiceService.FindExistingSessionAsync(deviceId).ConfigureAwait(true);
+                if (existing is not null)
+                {
+                    SessionId = existing.SessionId;
+                    Language = string.IsNullOrWhiteSpace(existing.Language) ? Language : existing.Language;
+                    IsSessionActive = true;
+                    LastTurnId = existing.LastTurnId ?? string.Empty;
+                    StatusText = $"Resumed session {SessionId} (turn {existing.TurnCounter})";
+                    GlobalStatusChanged?.Invoke(StatusText);
+                    _logger.LogInformation("Resumed existing voice session {SessionId} (turns={TurnCounter}, transcripts={TranscriptCount})",
+                        SessionId, existing.TurnCounter, existing.TranscriptCount);
+                    return;
+                }
+            }
+            catch (Exception ex)
+            {
+                _logger.LogWarning(ex, "Device session lookup failed, falling back to create");
+            }
+
+            // No existing session — create a new one
             GlobalStatusChanged?.Invoke("Creating voice session...");
             StatusText = "Creating voice session...";
             var response = await _voiceService.CreateSessionAsync(new McpVoiceSessionCreateRequest
             {
                 Language = Language,
                 ClientName = "RequestTracker.Android",
-                DeviceId = Environment.MachineName
+                DeviceId = deviceId
             }).ConfigureAwait(true);
 
             SessionId = response.SessionId;