fix(agent-core): add schema hints to tool arg errors

[tt-a1i]

Related Issue

Resolve #819

Problem

Tool argument validation errors currently say which argument is wrong, but not which names or types the model should use instead.

What changed

• Added schema-aware hints for unknown tool arguments, listing valid properties from the current object schema.
• Added expected type hints for missing required arguments when the schema declares a type.
• Kept generic AJV error formatting unchanged for other validation failures.
• Added coverage for the Read tool argument case, nested object properties, and schemas without an obvious type.

Validation

• pnpm --filter @moonshot-ai/agent-core exec vitest run test/tools/input-schema-io.test.ts
• pnpm --filter @moonshot-ai/agent-core run test
• pnpm --filter @moonshot-ai/agent-core run typecheck
• pnpm exec oxlint --type-aware packages/agent-core/src/tools/args-validator.ts packages/agent-core/test/tools/input-schema-io.test.ts --quiet
• pnpm --filter @moonshot-ai/agent-core run build
• git diff --check

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.

AI Assistance Disclosure

I used Codex to review the changes, sanity-check the implementation against existing patterns, and help spot potential edge cases.

[changeset-bot]

🦋 Changeset detected

Latest commit: 089d415

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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