Fix: Correct RPC method call in setSessionModel

[bliuk]

Description

This PR fixes a bug in ClientSideConnection.setSessionModel() where it incorrectly calls session/set_mode instead of session/set_model.

Problem

The setSessionModel() method was calling the wrong RPC method (session_set_mode), which caused parameter validation failures because the server expected modeId instead of
modelId.

Solution

Changed line 598 in src/acp.ts to call the correct RPC method: schema.AGENT_METHODS.session_set_model

Changes

• File: src/acp.ts
• Line: 598
• Change: session_set_mode → session_set_model

Code Diff

  async setSessionModel(
    params: schema.SetSessionModelRequest
  ): Promise<schema.SetSessionModelResponse> {
    return (
      (await this.#connection.sendRequest(
-       schema.AGENT_METHODS.session_set_mode,
+       schema.AGENT_METHODS.session_set_model,
        params
      )) ?? {}
    );
  }

[benbrandt]

Thanks for catching this!