Global --agent-file is silently ignored by kimi acp

kimi --agent-file /tmp/reviewer.md acp accepts the documented global option, but session/new binds the default agent profile. The appended instruction from the explicit agent file is absent from the persisted profile.bind.systemPrompt.

A minimal agent file:

---
name: reviewer
description: Review changes
---
${base_prompt}
Additional review instructions.

Reproduce without a model request: start ACP with the global option, call initialize and session/new, then inspect profile.bind. The tested native CLI version is 2.3.2. The current source also omits the root agent-file selection from ACP startup.

Expected: new ACP sessions use the launch-selected profile. Sessions loaded or resumed from disk keep their saved profile. Invalid explicit files should fail startup just as they do for the other CLI entry points.

A draft fix forwards the existing selection and the engine's existing mainAgentBinding input; it does not add an ACP extension or alter the default prompt. Is this eligible for an approved bug-fix contribution under the contribution policy?