fix(agent-core-v2): serialize agent startup

[chengluyu]

Related Issue

No linked issue. This is a focused fix for a reproducible v2 startup crash.

Problem

The agent lifecycle registered the main-agent handle before asynchronous bootstrap completed. Concurrent requests could therefore observe an agent whose activity lane was still initializing. A prompt submitted in that window could reject during loop launch and escape the fire-and-forget prompt scheduler, crashing the server. A failed bootstrap could also leave an unusable handle in the registry.

This happened reliably when the first prompt created a goal while the v2 agent was still starting.

What changed

• Make same-id agent creation single-flight and return only settled handles from readiness lookups.
• Make main-agent creation notification idempotent for concurrent callers.
• Remove and dispose partially bootstrapped handles after startup failure so later requests can retry cleanly.
• Settle synchronous prompt-launch failures as failed prompts instead of allowing an unhandled rejection.
• Add regression coverage for concurrent main-agent creation, readiness ordering, failed-bootstrap recovery, and prompt-launch failure.
• Add a patch changeset for @moonshot-ai/kimi-code.

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. No docs update is needed because this fixes a crash without changing commands, configuration, or documented usage.

[changeset-bot]

🦋 Changeset detected

Latest commit: 260623b

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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[pkg-pr-new]

pnpm dlx https://pkg.pr.new/@moonshot-ai/kimi-code@260623b

npx https://pkg.pr.new/@moonshot-ai/kimi-code@260623b

commit: 260623b