IRC App: Alt scrolls, Up/Down recall sent lines; /j for /join

- Alt + ; / Alt + . scroll the Buffer back and forward
- Up / Down (Fn + ; / Fn + .) browse the last 30 sent lines, shell-style,
  returning to the draft past the newest (InputHistory, host-tested)
- /j is short for /join

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/apps/irc_app.h

@@ -5,6 +5,7 @@
 
 #include "app.h"
 #include "event_bus.h"
+#include "input_history.h"
 #include "line_editor.h"
 #include "list_model.h"
 #include "services/irc_service.h"
@@ -48,6 +49,7 @@ class IrcApp : public App {
     uint32_t seenRevision_ = 0;
     IrcService::Status seenStatus_ = IrcService::Status::Stopped;
     LineEditor input_{400};
+    InputHistory history_{30};
     ListModel fields_{theme::kContent.h / theme::kLineHeight};
     bool editing_ = false;
     LineEditor fieldEditor_{63};