fix(agent-core): back off idle goal continuations

[xy200303]

Related Issue

Resolve #1977

Problem

When an active goal produces consecutive text-only turns while waiting on an external condition, the goal driver immediately launches another full-context model request. This can repeat indefinitely, consuming tokens and filling the context with no-op continuation history.

What changed

• Detect whether each goal turn invoked a tool and apply a 1-minute, 5-minute, then 15-minute capped backoff after two consecutive turns without tool progress.
• Reset the idle streak when tool progress resumes, wake the delay immediately when steered input arrives, keep the wait cancelable, and respect the remaining wall-clock budget.
• Add end-to-end coverage for exponential pacing, cancellation while waiting, and steer-triggered wake-up.

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: 071fa0c

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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