feat(clients): persist input settings, add mic input gain, fix iOS chat + VoiceOver

Input mode (VAD/PTT/Always-On), VAD threshold, and the new mic gain were
applied to the core + UI but never saved, so every relaunch reset to VAD
defaults. Each client now persists them and re-applies on connect:
  - iOS: UserDefaults (SessionState.loadAndApplyVoiceSettings + setter writes)
  - macOS: UserDefaults via MainWindowController didSet + loadPersistedAudioSettings
    (settings window also restores the VAD slider from the stored threshold)
  - Windows: new Models/VoiceSettings.cs (JSON at %AppData%\VoiceCat\voice.json,
    mirrors FeedbackSettings) loaded/applied in MainForm

Add global send-side mic gain API vc_set_input_gain (applied to MIC PCM in
on_capture_frame before the VAD gate, clamped to int16) + Swift/C# bindings,
and a 0-300% (default 100%) mic-volume slider on all three clients.

Fix iOS chat: ChatView called sendText(scope:.channel) with no targetId (0),
so channel messages went nowhere; now passes session.currentChannelId.

Fix iOS per-user tuning for VoiceOver: the tuning sheet was long-press
.contextMenu only (invisible to VoiceOver); UserRow now also exposes the same
buttons via .accessibilityActions (no visual change).

Verified: core builds clean; ctest 24/27 (3 pre-existing teardown crashes,
reproduced with changes stashed); VoiceCatMac + VoiceCatiOS (arm64 sim) build
SUCCEEDED; VoiceCat.Interop dotnet build succeeded. Windows App not built
(WinForms can't build on macOS) — follows existing patterns.

clients/windows/VoiceCat.App/Forms/MainForm.Designer.cs

@@ -51,6 +51,8 @@ partial class MainForm
     private ProgressBar pbLevel = null!;
     private Label lblVadThreshold = null!;
     private TrackBar trkVadThreshold = null!;
+    private Label lblMicGain = null!;
+    private TrackBar trkMicGain = null!;
 
     protected override void Dispose(bool disposing)
     {
@@ -94,6 +96,8 @@ partial class MainForm
         pbLevel = new ProgressBar();
         lblVadThreshold = new Label();
         trkVadThreshold = new TrackBar();
+        lblMicGain = new Label();
+        trkMicGain = new TrackBar();
         menuStrip = new MenuStrip();
         toolStrip = new ToolStrip();
         tsbJoinVoice = new ToolStripButton();
@@ -336,6 +340,23 @@ partial class MainForm
         trkVadThreshold.TabIndex = 9;
         trkVadThreshold.Visible = true;
 
+        lblMicGain.Text = "Mic volume:";
+        lblMicGain.AutoSize = true;
+        lblMicGain.Margin = new Padding(12, 5, 4, 0);
+
+        trkMicGain.AccessibleName = "Microphone volume";
+        trkMicGain.AccessibleDescription =
+            "Boost a quiet microphone. 100 is unity; range 0–300 percent.";
+        trkMicGain.Minimum = 0;
+        trkMicGain.Maximum = 300;
+        trkMicGain.Value = 100;
+        trkMicGain.TickFrequency = 25;
+        trkMicGain.SmallChange = 5;
+        trkMicGain.LargeChange = 25;
+        trkMicGain.Width = 120;
+        trkMicGain.Margin = new Padding(0, 2, 0, 0);
+        trkMicGain.TabIndex = 10;
+
         flpVoiceBottom.Dock = DockStyle.Fill;
         flpVoiceBottom.Padding = new Padding(4, 0, 4, 2);
         flpVoiceBottom.Controls.Add(lblInputDevice);
@@ -345,6 +366,8 @@ partial class MainForm
         flpVoiceBottom.Controls.Add(pbLevel);
         flpVoiceBottom.Controls.Add(lblVadThreshold);
         flpVoiceBottom.Controls.Add(trkVadThreshold);
+        flpVoiceBottom.Controls.Add(lblMicGain);
+        flpVoiceBottom.Controls.Add(trkMicGain);
 
         pnlVoice.Dock = DockStyle.Bottom;
         pnlVoice.Height = 68;

clients/windows/VoiceCat.App/Forms/MainForm.cs

@@ -1,4 +1,5 @@
 using VoiceCat.App.Audio;
+using VoiceCat.App.Models;
 using VoiceCat.App.Notifications;
 using VoiceCat.Interop;
 
@@ -14,6 +15,7 @@ public partial class MainForm : Form
     private readonly string _nickname;
     private readonly System.Windows.Forms.Timer _pumpTimer = new() { Interval = 30 };
     private readonly EventFeedback _feedback = new(FeedbackSettings.Load());
+    private readonly VoiceSettings _voiceSettings = VoiceSettings.Load();
 
     // Channel / user state
     private uint _currentChannelId;
@@ -85,6 +87,7 @@ public partial class MainForm : Form
         radioPtt.CheckedChanged += RadioPtt_CheckedChanged;
         radioAlwaysOn.CheckedChanged += RadioAlwaysOn_CheckedChanged;
         trkVadThreshold.Scroll += TrkVadThreshold_Scroll;
+        trkMicGain.Scroll += TrkMicGain_Scroll;
         btnChangePtt.Click += BtnChangePtt_Click;
         btnRefreshDevices.Click += (_, _) => LoadInputDevices();
         cboInputDevice.SelectedIndexChanged += CboInputDevice_SelectedIndexChanged;
@@ -98,9 +101,33 @@ public partial class MainForm : Form
             if (_micStreamId != 0) _client.SetPushToTalk(false);
         };
 
+        ApplyPersistedVoiceSettings();
         BootstrapFromServer();
     }
 
+    /// <summary>
+    /// Restore the saved transmission mode / VAD sensitivity / mic gain / PTT key into the UI so a
+    /// relaunch keeps the user's input settings instead of resetting to the designer defaults. The
+    /// values are pushed into the core when the mic stream starts (<see cref="BtnMicToggle_Click"/>).
+    /// Setting the radio fires CheckedChanged, which only adjusts visibility while the mic is idle.
+    /// </summary>
+    private void ApplyPersistedVoiceSettings()
+    {
+        _pttKey = (Keys)_voiceSettings.PttKey;
+
+        trkVadThreshold.Value = Math.Clamp(_voiceSettings.VadThresholdSlider,
+                                           trkVadThreshold.Minimum, trkVadThreshold.Maximum);
+        trkMicGain.Value = Math.Clamp(_voiceSettings.MicGain,
+                                      trkMicGain.Minimum, trkMicGain.Maximum);
+
+        switch ((VcInputMode)_voiceSettings.InputMode)
+        {
+            case VcInputMode.PushToTalk: radioPtt.Checked = true; break;
+            case VcInputMode.AlwaysOn:   radioAlwaysOn.Checked = true; break;
+            default:                     radioVad.Checked = true; break;
+        }
+    }
+
     // ── Startup ──────────────────────────────────────────────────────────────
 
     private void BootstrapFromServer()
@@ -661,6 +688,7 @@ public partial class MainForm : Form
                     _client.SetInputDevice(streamId, dev.Id);
                 _client.SetInputMode(CurrentInputMode());
                 if (radioVad.Checked) _client.SetVadThreshold(VadThresholdFromSlider());
+                _client.SetInputGain(trkMicGain.Value / 100f);
                 SetVoiceJoinedState(true);
                 AddActivity("Joined voice — microphone active");
                 _feedback.PlaySound(SoundEvent.VoiceOn);
@@ -779,6 +807,7 @@ public partial class MainForm : Form
         btnChangePtt.Visible = false;
         lblVadThreshold.Visible = true;
         trkVadThreshold.Visible = true;
+        SaveInputMode(VcInputMode.VoiceActivation);
         if (_micStreamId != 0)
         {
             _client.SetInputMode(VcInputMode.VoiceActivation);
@@ -794,6 +823,7 @@ public partial class MainForm : Form
         btnChangePtt.Visible = true;
         lblVadThreshold.Visible = false;
         trkVadThreshold.Visible = false;
+        SaveInputMode(VcInputMode.PushToTalk);
         if (_micStreamId != 0)
         {
             _client.SetInputMode(VcInputMode.PushToTalk);
@@ -808,15 +838,31 @@ public partial class MainForm : Form
         btnChangePtt.Visible = false;
         lblVadThreshold.Visible = false;
         trkVadThreshold.Visible = false;
+        SaveInputMode(VcInputMode.AlwaysOn);
         if (_micStreamId != 0) _client.SetInputMode(VcInputMode.AlwaysOn);
     }
 
     private void TrkVadThreshold_Scroll(object? sender, EventArgs e)
     {
+        _voiceSettings.VadThresholdSlider = trkVadThreshold.Value;
+        _voiceSettings.Save();
         if (_micStreamId != 0 && radioVad.Checked)
             _client.SetVadThreshold(VadThresholdFromSlider());
     }
 
+    private void TrkMicGain_Scroll(object? sender, EventArgs e)
+    {
+        _voiceSettings.MicGain = trkMicGain.Value;
+        _voiceSettings.Save();
+        if (_micStreamId != 0) _client.SetInputGain(trkMicGain.Value / 100f);
+    }
+
+    private void SaveInputMode(VcInputMode mode)
+    {
+        _voiceSettings.InputMode = (int)mode;
+        _voiceSettings.Save();
+    }
+
     private float VadThresholdFromSlider() =>
         0.1f * (1f - (trkVadThreshold.Value - 1f) / 99f);
 
@@ -832,6 +878,8 @@ public partial class MainForm : Form
         {
             _pttKey = dlg.CapturedKey;
             lblPttKey.Text = $"({_pttKey})";
+            _voiceSettings.PttKey = (int)_pttKey;
+            _voiceSettings.Save();
         }
     }
 

clients/windows/VoiceCat.App/Models/VoiceSettings.cs

@@ -0,0 +1,53 @@
+using System.Text.Json;
+
+namespace VoiceCat.App.Models;
+
+/// <summary>
+/// User's send-side voice input preferences — transmission mode, VAD sensitivity, mic input
+/// gain, and the push-to-talk key. Persisted to %AppData%\VoiceCat\voice.json, same pattern as
+/// <see cref="ServerListStore"/> and FeedbackSettings: a missing or corrupt file yields defaults
+/// rather than throwing. Slider-position values are stored as-is so MainForm can restore the
+/// TrackBars directly.
+/// </summary>
+public sealed class VoiceSettings
+{
+    /// <summary>Transmission mode: 0 = voice activation, 1 = push-to-talk, 2 = always on
+    /// (matches Interop's VcInputMode).</summary>
+    public int InputMode { get; set; } = 0;
+
+    /// <summary>VAD sensitivity slider position, 1–100 (default mirrors the designer's 76).</summary>
+    public int VadThresholdSlider { get; set; } = 76;
+
+    /// <summary>Microphone input gain slider position, 0–300 percent (100 = unity).</summary>
+    public int MicGain { get; set; } = 100;
+
+    /// <summary>Push-to-talk key, stored as the integer value of System.Windows.Forms.Keys.</summary>
+    public int PttKey { get; set; } = (int)Keys.F8;
+
+    private static readonly JsonSerializerOptions JsonOptions = new() { WriteIndented = true };
+
+    private static string AppDataDir => Path.Combine(
+        Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "VoiceCat");
+
+    private static string FilePath => Path.Combine(AppDataDir, "voice.json");
+
+    public static VoiceSettings Load()
+    {
+        try
+        {
+            if (!File.Exists(FilePath)) return new VoiceSettings();
+            string json = File.ReadAllText(FilePath);
+            return JsonSerializer.Deserialize<VoiceSettings>(json) ?? new VoiceSettings();
+        }
+        catch
+        {
+            return new VoiceSettings();
+        }
+    }
+
+    public void Save()
+    {
+        Directory.CreateDirectory(AppDataDir);
+        File.WriteAllText(FilePath, JsonSerializer.Serialize(this, JsonOptions));
+    }
+}