fix(acp): fallback unknown turn end reasons

[tt-a1i]

Summary

• return end_turn for unexpected runtime turn-end reasons instead of falling through to undefined
• add focused coverage for known reasons and the unknown fallback path

Related Issue

Addresses #837 finding 6.

Tests

• pnpm --filter @moonshot-ai/acp-adapter exec vitest run test/events-map.test.ts
• pnpm --filter @moonshot-ai/acp-adapter run test
• pnpm --filter @moonshot-ai/acp-adapter run typecheck
• pnpm --filter @moonshot-ai/acp-adapter run build
• pnpm --filter @moonshot-ai/kimi-code run typecheck
• pnpm exec oxlint --type-aware packages/acp-adapter/src/events-map.ts packages/acp-adapter/test/events-map.test.ts --quiet
• git diff --check

AI Assistance Disclosure

I used Codex to review the changes, sanity-check the implementation against existing patterns, and help spot potential edge cases.

[changeset-bot]

🦋 Changeset detected

Latest commit: 48178d4

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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