fix(kosong): abort stalled model streams

[crow-1412]

Related Issue

Resolve #1050

Related to #2570.

Problem

Model requests could remain pending forever while waiting for response headers, the first streamed part, or the next streamed part. The generation drivers used unbounded awaits, so the caller could not recover from a silent connection without cancelling or restarting the session.

What changed

• bound response-header and first-part waits at five minutes, while enforcing a 30-second idle deadline between streamed parts
• abort the provider request and close acquired or late streams when a deadline or caller cancellation fires
• surface the existing retryable APITimeoutError, preserving the repository's retry behavior and the caller's AbortError
• apply the behavior to both v2 and legacy generation drivers
• cover header stalls, mid-stream stalls, callback failures, cancellation, and exactly-once stream cleanup

Validation

• @moonshot-ai/agent-core-v2 generate contract tests: 15 passed
• @moonshot-ai/kosong generate tests: 37 passed
• both affected packages typecheck
• v2 import-boundary check passes
• type-aware lint reports no warnings or errors on the changed TypeScript files
• changeset status reports a patch bump for @moonshot-ai/kimi-code

A full v2 suite run was also attempted; the remaining failures are unrelated current-main image-compression timeout, performance-baseline, and full-compaction cases outside these paths.

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: 13c6dbc

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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