fix: report task stop reasons to the model

[kermanx]

Related Issue

None; the problem is described below.

Problem

When a subagent or another managed task stopped before completion, the model-facing result did not consistently explain who stopped it or preserve a non-user stop reason. In particular, a task cancelled manually through the task API could reach the model as a generic killed task, making user intent indistinguishable from system failure.

What changed

• Added an explicit stopByUser task operation that keeps user cancellation represented by the existing typed cancellation reason inside agent-core-v2.
• Propagated manual cancellation from RPC and the REST task-cancel route through that operation.
• Updated foreground subagent failures and background task notifications to say when the user stopped the work and to include other recorded stop reasons.
• Added regression coverage for foreground subagents, background process notifications, Bash interruption, task tools, and the REST cancellation route.

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. Added a patch changeset for @moonshot-ai/kimi-code.
• Ran gen-docs skill, or this PR needs no doc update. No docs update is needed because commands, configuration, and user workflows are unchanged; only model-facing task termination context changes.

Validation

• pnpm --filter @moonshot-ai/agent-core-v2 typecheck
• pnpm --filter @moonshot-ai/kap-server typecheck
• pnpm --filter @moonshot-ai/agent-core-v2 lint:domain
• pnpm --filter @moonshot-ai/agent-core-v2 exec vitest run test/tool/tool.test.ts test/agent/task/rpc-events.test.ts test/agent/task/taskManager.test.ts test/agent/task/tools/task-tools.test.ts test/os/backends/node-local/tools/bash.test.ts
• pnpm --filter @moonshot-ai/kap-server exec vitest run test/tasks.test.ts

[changeset-bot]

🦋 Changeset detected

Latest commit: e25405b

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@e25405b

npx https://pkg.pr.new/@moonshot-ai/kimi-code@e25405b

commit: e25405b