Fix connect-time username prompt being unreachable for SSH/RDP

validateProfileForConnect() still hard-failed with a blocking
QMessageBox for a blank SSH/RDP username, running before
requestConnectOptions() ever got a chance to prompt for it inline --
so the connect-time username prompt added for issue #21 was dead code
in practice; users just got told to go edit the profile instead.

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

docs/PROGRESS.md

@@ -184,6 +184,15 @@ Delivered:
   through the dialog), so importing any SSH/RDP entry without a
   username still failed outright until this second check was found and
   removed too
+- A third, independent username check was still live even after the two
+  above were removed: `SessionTab::validateProfileForConnect()` (run at
+  the very top of `connectSession()`/`reconnectSession()`, before
+  `requestConnectOptions()` ever gets a chance to run its async prompt)
+  had its own hard-fail "SSH/RDP username is required" `QMessageBox`,
+  so a blank-username profile still couldn't connect at all -- it just
+  told the user to go edit the profile instead of ever prompting inline.
+  Removed; connect-time prompting is now the only username gate for
+  SSH/RDP
 - Robustness fix: an unrecognized `FramebufferUpdate` rectangle encoding
   used to abort the connection generically; `kAnnouncedEncodings` is now
   the single source of truth for what `SetEncodings` announces and what