test(native): make path helper expectations platform-aware

[haosenwang1018]

Related Issue

Part of #225

Problem

The native path helper tests expected absolute paths by interpolating ${appRoot}/... with POSIX separators. The helpers themselves correctly use node:path.resolve(), so they return native \ separators on Windows. That makes the test fail on Windows even though the implementation is behaving as intended.

What changed

• Added a small underAppRoot() test helper that builds expected absolute paths with node:path.resolve().
• Updated filesystem path expectations to use the helper.
• Left nativeManifestKey() expectations unchanged because manifest keys are artifact keys, not native filesystem paths.
• Added an empty changeset because this is a test-only portability fix with no published package bump.

Verification

• pnpm --filter @moonshot-ai/kimi-code exec vitest run test/scripts/native/paths.test.ts
• pnpm --filter @moonshot-ai/kimi-code run typecheck
• pnpm exec oxlint apps/kimi-code/test/scripts/native/paths.test.ts
• pnpm --filter @moonshot-ai/kimi-code run test
• pnpm changeset status --since=origin/main

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: ced5f90

The changes in this PR will be included in the next version bump.

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