Keep the composer focused after sending with the return key (#1490)

* Keep the composer focused after sending with the return key

On iOS, return sends and then drops the keyboard, so every message in a
back-and-forth costs an extra tap to reopen it. sendMessage() is the
onSubmit handler; reasserting the FocusState there keeps the keyboard up
between messages. macOS already refocuses on appear and is unaffected.

Fixes #457

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

* Address Codex review: refocus only on return-key submission

The reassert moves from sendMessage() into the TextField's onSubmit, so
the send button no longer reopens a deliberately dismissed keyboard on
iOS and never moves focus on macOS.

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

---------

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

bitchat/Views/ContentComposerView.swift

@@ -73,7 +73,14 @@ struct ContentComposerView: View {
                 .textInputAutocapitalization(.sentences)
                 #endif
                 .submitLabel(.send)
-                .onSubmit(onSendMessage)
+                .onSubmit {
+                    onSendMessage()
+                    // Only the return-key path: it steals focus on iOS, so
+                    // every message would cost a tap to reopen the keyboard.
+                    // The send button must not reopen a deliberately
+                    // dismissed keyboard, so it stays out of this.
+                    isTextFieldFocused.wrappedValue = true
+                }
                 .padding(.vertical, theme.usesGlassChrome ? 8 : 4)
                 .padding(.horizontal, 6)
                 .themedInputBackground()