test(agent-core): normalize skill scanner path expectations

[haosenwang1018]

Related Issue

Part of #225.

Problem

resolveSkillRoots() normalizes filesystem realpaths to forward slashes before returning skill root paths. The skill scanner tests compared those returned paths against raw fs.realpath() output, which is native-path formatted on Windows and can contain backslashes. That makes the tests fail on Windows even though the product behavior is intentionally normalized.

What changed

• Added a small normalizedRealpath() test helper that mirrors the production path normalization.
• Updated skill-root path assertions to compare against normalized expected paths.
• Added an empty changeset because this is test-only.

Verification

• pnpm exec vitest run packages/agent-core/test/skill/scanner.test.ts
• pnpm --filter @moonshot-ai/agent-core typecheck
• pnpm --filter @moonshot-ai/agent-core test
• pnpm changeset status --since origin/main
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: beb927d

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

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