fix(acp): support relayed stdio MCP servers

[Fnine59]

Related Issue

Fixes #3069

Problem

The native kimi acp path uses @moonshot-ai/acp-server, whose current converter lives in packages/acp-server/src/convert.ts. It rejects ACP's type-absent stdio MCP branch because ephemeral session overlays require an explicit runtime identity, so clients receive an internal error before session/new or session/load can finish.

What changed

• Convert type-absent ACP stdio entries into the engine's stdio configuration while preserving command, arguments, and environment variables.
• Bind these relayed processes explicitly to the workspace's local runtime, which supports bidirectional stdio, without weakening the session overlay's runtime identity requirement.
• Keep the existing HTTP, SSE, and unsupported ACP transport behavior unchanged.
• Add converter coverage plus lifecycle coverage that connects a real stdio MCP fixture through session/new and session/load after restart.

Tests

• pnpm --filter @moonshot-ai/acp-server test (146 passed)
• pnpm --filter @moonshot-ai/acp-server typecheck
• pnpm exec oxlint --type-aware packages/acp-server/src/convert.ts packages/acp-server/test/convert.test.ts packages/acp-server/test/lifecycle.test.ts
• git diff --check

Checklist

• I have read the CONTRIBUTING document.
• I have linked a related issue, or explained the problem above.
• I have added tests that prove my feature works.
• Ran gen-changesets skill, or this PR needs no changeset.
• Ran gen-docs skill, or this PR needs no doc update.

[changeset-bot]

🦋 Changeset detected

Latest commit: 00491cc

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@moonshot-ai/kimi-code	Patch

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