fix(agent-core): recover from unsupported image_url variants

[030611]

Related Issue

Resolve #2759

Problem

During context compaction, text-only providers can reject retained image blocks with unknown variant image_url, expected text. This diagnostic was not classified as an image-format error, so the existing media-stripped retry did not run.

What changed

• Recognize the provider diagnostic in isImageFormatError.
• Cover it in the classifier test and the full-compaction recovery test.
• Add a patch changeset for the CLI behavior fix.

Tests:

• pnpm --filter @moonshot-ai/agent-core-v2 test -- test/kosong/contract/errors.test.ts test/agent/fullCompaction/fullCompaction.test.ts (89 passed)
• pnpm --filter @moonshot-ai/agent-core-v2 lint:imports
• pnpm --filter @moonshot-ai/agent-core-v2 typecheck
• pnpm exec oxlint on the changed TypeScript files

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: fdfa8ab

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

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR