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

test/test_irc_session/test_irc_session.cpp

@@ -333,6 +333,16 @@ void test_server_buffer_never_counts_as_unread() {
     TEST_ASSERT_EQUAL(0, f.session->totalUnread());
 }
 
+void test_revision_changes_when_something_visible_changes() {
+    Fixture f;
+    f.registerNow();
+    uint32_t r = f.session->revision();
+    f.recv("PING :x");  // nothing visible
+    TEST_ASSERT_EQUAL_UINT32(r, f.session->revision());
+    f.recv(":roro!u@h JOIN #roro");
+    TEST_ASSERT_TRUE(f.session->revision() != r);
+}
+
 int main() {
     UNITY_BEGIN();
     RUN_TEST(test_plain_registration_sends_nick_and_user);
@@ -360,5 +370,6 @@ int main() {
     RUN_TEST(test_buffer_keeps_only_recent_lines);
     RUN_TEST(test_quit_is_forgotten_once_disconnected);
     RUN_TEST(test_server_buffer_never_counts_as_unread);
+    RUN_TEST(test_revision_changes_when_something_visible_changes);
     return UNITY_END();
 }