Move exec to HookAPI, sessionManager/modelRegistry to HookEventContext

Breaking changes:
- HookEventContext now has sessionManager and modelRegistry (moved from SessionEventBase)
- HookAPI now has exec() method (moved from HookEventContext/HookCommandContext)
- HookRunner constructor takes sessionManager and modelRegistry as required params
- Session events no longer include sessionManager/modelRegistry fields

Hook code migration:
- event.sessionManager -> ctx.sessionManager
- event.modelRegistry -> ctx.modelRegistry
- ctx.exec() -> pi.exec()

Updated:
- src/core/hooks/types.ts - type changes
- src/core/hooks/runner.ts - constructor, createContext
- src/core/hooks/loader.ts - add exec to HookAPI
- src/core/sdk.ts - pass sessionManager/modelRegistry to HookRunner
- src/core/agent-session.ts - remove sessionManager/modelRegistry from events
- src/modes/* - remove setSessionFile calls, update events
- examples/hooks/* - update to new API

packages/coding-agent/examples/hooks/confirm-destructive.ts

@@ -29,7 +29,7 @@ export default function (pi: HookAPI) {
 			if (!ctx.hasUI) return;
 
 			// Check if there are unsaved changes (messages since last assistant response)
-			const entries = event.sessionManager.getEntries();
+			const entries = ctx.sessionManager.getEntries();
 			const hasUnsavedWork = entries.some(
 				(e): e is SessionMessageEntry => e.type === "message" && e.message.role === "user",
 			);