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.App/Forms/ServerIdentityDialog.cs

@@ -3,7 +3,7 @@ using VoiceCat.Interop;
 namespace VoiceCat.App.Forms;
 
 /// <summary>
-/// TOFU server-identity confirmation (M4). Shown only for VcTofuStatus.FirstConnect/Mismatch
+/// TOFU server-identity confirmation. Shown only for VcTofuStatus.FirstConnect/Mismatch
 /// — never Matched (that's the silent-success "subsequent connects verify the pin" path
 /// docs/security.md describes; showing a dialog on every routine reconnect would be exactly
 /// the "overly chatty" experience this project avoids elsewhere too).