fix(agent-core-v2): flush wire before agent disposal

[LouisDM]

Related Issue

Refs #2727

Problem

Agent removal waits for active turns and compaction, but it can dispose the agent scope before queued replayable wire records are flushed. In ACP, this allows session/close to return while the latest assistant content is not yet durable.

On current main, the normal-speed prompt/close path did not reproduce persistent loss. A controlled delayed wire append did reproduce the lifecycle race: agent removal completed before the final records were durable.

What changed

• Flush the per-agent replayable wire after turns and compaction settle, before disposing the child scope.
• Guarantee scope cleanup and the disposal event even if the flush rejects, while preserving that error for the caller.
• Add regression tests proving both the wait barrier and the rejecting-flush cleanup path.
• Add a patch changeset for @moonshot-ai/kimi-code.

This closes the verified close/dispose durability gap without claiming to explain every persistent-history symptom reported in #2727.

Validation

• pnpm --filter @moonshot-ai/agent-core-v2 exec vitest run test/session/agentLifecycle/agentLifecycle.test.ts (29 passed)
• pnpm --filter @moonshot-ai/acp-server exec vitest run test/close.test.ts test/lifecycle.test.ts (18 passed)
• pnpm --filter @moonshot-ai/agent-core-v2 typecheck
• pnpm --filter @moonshot-ai/acp-server typecheck
• pnpm --filter @moonshot-ai/agent-core-v2 lint:imports (1135 files checked)
• pnpm exec oxlint packages/agent-core-v2/src/session/agentLifecycle/agentLifecycleService.ts packages/agent-core-v2/test/session/agentLifecycle/agentLifecycle.test.ts
• pnpm changeset status --since=origin/main

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: 1a0b873

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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