Integrates the ai_client.events emitter into the gui_2.py App class. Adds a new test file to verify that the App subscribes to API lifecycle events upon initialization. This is the first step in aligning gui_2.py with the project's event-driven architecture.
- Port 10 missing features from gui.py to gui_2.py: performance
diagnostics, prior session log viewing, token budget visualization,
agent tools config, API hooks server, GUI task queue, discussion
truncation, THINKING/LIVE indicators, event subscriptions, and
session usage tracking
- Persist window visibility state in config.toml
- Fix Gemini cache invalidation by separating discussion history
from cached context (use MD5 hash instead of built-in hash)
- Add cost optimizations: tool output truncation at source, proactive
history trimming at 40%, summary_only support in aggregate.run()
- Add cleanup() for destroying API caches on exit
