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/NativeMethods.cs

@@ -148,7 +148,7 @@ internal static partial class NativeMethods
     [LibraryImport(LibName)]
     internal static partial void vc_free_device_list(ref VcDeviceListNative list);
 
-    // ── M4: channel / user / stream snapshot getters ────────────────────────────────────────
+    // ── Channel / user / stream snapshot getters ────────────────────────────────────────────
     [LibraryImport(LibName)]
     internal static partial VcResult vc_list_channels(nint c, out VcChannelListNative outList);
 
@@ -168,7 +168,7 @@ internal static partial class NativeMethods
     [LibraryImport(LibName)]
     internal static partial void vc_free_stream_summary_list(ref VcStreamSummaryListNative list);
 
-    // ── M4: TOFU server-identity gate ───────────────────────────────────────────────────────
+    // ── TOFU server-identity gate ───────────────────────────────────────────────────────────
     [LibraryImport(LibName)]
     internal static partial VcResult vc_confirm_server_identity(nint c, int accept);
 
@@ -176,7 +176,7 @@ internal static partial class NativeMethods
     internal static partial VcResult vc_get_server_identity_display(nint c, nint outBuf,
         nuint bufCap, out nuint outLen);
 
-    // ── M5: Moderation & admin ─────────────────────────────────────────────────────────────
+    // ── Moderation & admin ───────────────────────────────────────────────────────────────────
     [LibraryImport(LibName, StringMarshalling = StringMarshalling.Utf8)]
     internal static partial VcResult vc_kick_user(nint c, uint userId, string? reason);