Add custom session events for thinking level and model changes

Session manager changes:
- Add ThinkingLevelChangeEntry and ModelChangeEntry types
- Add saveThinkingLevelChange() and saveModelChange() methods
- Update loadThinkingLevel() to also check for thinking_level_change events
  (not just session headers)

TUI changes:
- Pass SessionManager to TuiRenderer constructor
- Call saveThinkingLevelChange() when user changes thinking level via /thinking
- Store session manager as instance variable for future use

This ensures thinking level changes during a session are persisted
and correctly restored on --continue.

packages/coding-agent/src/main.ts

@@ -114,8 +114,8 @@ Guidelines:
 
 Current directory: ${process.cwd()}`;
 
-async function runInteractiveMode(agent: Agent, _sessionManager: SessionManager, version: string): Promise<void> {
-	const renderer = new TuiRenderer(agent, version);
+async function runInteractiveMode(agent: Agent, sessionManager: SessionManager, version: string): Promise<void> {
+	const renderer = new TuiRenderer(agent, sessionManager, version);
 
 	// Initialize TUI
 	await renderer.init();