fix: correct RPC method call in ClientSideConnection.setSessionModel() (#7)

The setSessionModel method was incorrectly calling session_set_mode
instead of session_set_model, causing parameter validation errors.

Changed line 598 in src/acp.ts to use the correct RPC method.

Fixes: Parameter validation error when calling setSessionModel()

Author: bliuk

src/acp.ts

@@ -595,7 +595,7 @@ export class ClientSideConnection implements Agent {
   ): Promise<schema.SetSessionModelResponse> {
     return (
       (await this.#connection.sendRequest(
-        schema.AGENT_METHODS.session_set_mode,
+        schema.AGENT_METHODS.session_set_model,
         params,
       )) ?? {}
     );