fix(coding-agent): save initial model and thinking level to session

When creating a new session, initial model and thinking level were set
on the agent but never saved to session file. This caused --resume to
default thinking level to 'off'.

fixes #342

packages/coding-agent/src/core/sdk.ts

@@ -621,6 +621,12 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 	// Restore messages if session has existing data
 	if (hasExistingSession) {
 		agent.replaceMessages(existingSession.messages);
+	} else {
+		// Save initial model and thinking level for new sessions so they can be restored on resume
+		if (model) {
+			sessionManager.appendModelChange(model.provider, model.id);
+		}
+		sessionManager.appendThinkingLevelChange(thinkingLevel);
 	}
 
 	const session = new AgentSession({