M1 step 5: IRC App

- Chat: header (Buffer n/N, unread elsewhere, topic or connection
  state), wrapped hh:mm <nick> lines (own in accent, Mentions green,
  info grey), input line; Tab cycles Buffers, Fn+Up/Down scrolls back,
  Enter sends, Back leaves while the IRC Service keeps running
- /settings: server form (host, port, TLS, self-signed pinning, nick,
  SASL, NickServ, auto-join); Save & reconnect restarts the session
- Opening the App starts the IRC Service; viewing a Buffer clears its
  unread count; IrcSession gains a revision counter for redraws

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

lib/irc/src/irc_session.h

@@ -68,6 +68,8 @@ class IrcSession {
     int bufferCount() const { return static_cast<int>(buffers_.size()); }
     const IrcBuffer& buffer(int i) const { return buffers_[i]; }
     int totalUnread() const;
+    // Changes whenever a Buffer gains a line or changes, so a view knows when to redraw.
+    uint32_t revision() const { return revision_; }
 
     IrcEffects takeEffects();
 
@@ -93,6 +95,7 @@ class IrcSession {
     std::set<std::string> namesRequested_;
     std::vector<std::string> rejoin_;  // IRC channels to join again after a reconnect
     IrcEffects effects_;
+    uint32_t revision_ = 0;
 };
 
 }  // namespace roro