chore: comment cleanup pass ahead of open-sourcing

Removes leftover debug scaffolding (stray Console.WriteLine/NSLog traces,
dead nick_buf_ptr, a no-op --print-config flag now implemented for real),
fixes stale/misleading comments (channel passwords are no longer a "future
M5+" feature, a wrong cross-reference, a stale TlsContext::close() mention,
an incomplete BanRecord::subject_type doc, and a smoke test pointing at a
build/m1-dev preset that no longer exists), strips internal M1-M5 milestone
jargon from comments now that the roadmap is done, trims comments that just
restated the following line, and consolidates a few "why" explanations that
were duplicated 2-3 times in the same file.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

clients/windows/VoiceCat.Interop/VoiceCatClient.cs

@@ -95,10 +95,6 @@ public sealed class VoiceCatClient : IDisposable
 
     internal void EnqueueEvent(VoiceCatEvent ev)
     {
-        // Temporary diagnostic (manual debugging session) — confirms the native callback
-        // chain (UnmanagedCallersOnly -> GCHandle resolve -> here) actually fires, independent
-        // of whether the UI-thread drain (PumpEvents) ever sees it.
-        Console.WriteLine($"[VoiceCatClient] EnqueueEvent (native thread): {ev}");
         _events.Writer.TryWrite(ev);
     }
     internal void EnqueueLevel(uint streamId, float rms) => _latestLevels[streamId] = rms;
@@ -116,7 +112,7 @@ public sealed class VoiceCatClient : IDisposable
     public VcResult AuthenticateUser(string username, string password) =>
         NativeMethods.vc_authenticate_user(_handle.DangerousGetHandle(), username, password);
 
-    // ── TOFU server-identity gate (M4) ──────────────────────────────────────────────────────
+    // ── TOFU server-identity gate ───────────────────────────────────────────────────────────
     public VcResult ConfirmServerIdentity(bool accept) =>
         NativeMethods.vc_confirm_server_identity(_handle.DangerousGetHandle(), accept ? 1 : 0);
 
@@ -143,9 +139,7 @@ public sealed class VoiceCatClient : IDisposable
 
     // ── Channels ─────────────────────────────────────────────────────────────────────────
     /// <summary>Result arrives as a VcEventType.JoinResult event, not via this return value
-    /// (which only reflects "request queued" — see voicecat.h's vc_join_channel doc comment).
-    /// NOTE: no in-tree channel has a server-side password to check yet (M5+ feature) — this
-    /// path is wired but not yet exercisable end-to-end.</summary>
+    /// (which only reflects "request queued" — see voicecat.h's vc_join_channel doc comment).</summary>
     public VcResult JoinChannel(uint channelId, string? password = null) =>
         NativeMethods.vc_join_channel(_handle.DangerousGetHandle(), channelId, password);
 
@@ -290,7 +284,7 @@ public sealed class VoiceCatClient : IDisposable
     public VcResult SetPcmSink(nint cb, IntPtr user) =>
         NativeMethods.vc_set_pcm_sink(_handle.DangerousGetHandle(), cb, user);
 
-    // ── M5: Moderation & admin ───────────────────────────────────────────────────────────
+    // ── Moderation & admin ───────────────────────────────────────────────────────────────
     public VcResult KickUser(uint userId, string? reason = null) =>
         NativeMethods.vc_kick_user(_handle.DangerousGetHandle(), userId, reason);