Refactor SessionEventBase to pass sessionManager and modelRegistry

Breaking changes to hook types:
- SessionEventBase now passes sessionManager and modelRegistry directly
- before_compact: passes preparation, previousCompactions (newest first)
- before_switch: has targetSessionFile; switch: has previousSessionFile
- Removed resolveApiKey (use modelRegistry.getApiKey())
- getSessionFile() returns string | undefined for in-memory sessions

Updated:
- All session event emissions in agent-session.ts
- Hook examples (custom-compaction.ts, auto-commit-on-exit.ts, confirm-destructive.ts)
- Tests (compaction-hooks.test.ts, compaction-hooks-example.test.ts)
- export-html.ts guards for in-memory sessions

packages/coding-agent/examples/hooks/auto-commit-on-exit.ts

@@ -20,9 +20,10 @@ export default function (pi: HookAPI) {
 		}
 
 		// Find the last assistant message for commit context
+		const entries = event.sessionManager.getEntries();
 		let lastAssistantText = "";
-		for (let i = event.entries.length - 1; i >= 0; i--) {
-			const entry = event.entries[i];
+		for (let i = entries.length - 1; i >= 0; i--) {
+			const entry = entries[i];
 			if (entry.type === "message" && entry.message.role === "assistant") {
 				const content = entry.message.content;
 				if (Array.isArray(content)) {