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/PasswordPromptDialog.cs

@@ -1,7 +1,7 @@
 namespace VoiceCat.App.Forms;
 
 /// <summary>Small modal for "type a password right now" — used when a saved server's
-/// password wasn't remembered, and (Phase E) for password-protected channel joins.</summary>
+/// password wasn't remembered, and for password-protected channel joins.</summary>
 public partial class PasswordPromptDialog : Form
 {
     public string Password => txtPassword.Text;