Changes: - Remove test_reminder behavior (debug artifact) - System tray notifications via QSystemTrayIcon.showMessage() - IM-style chat bubbles: QLabel pool, tight grouping, tail corners - Thread safety fix: QThread.currentThread() in add_message() - docs: complete debug journal (11 sections, from first segfault to final fix) Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>