Stabilize skill loader test isolation

[stamsam]

Summary

• Narrow the prompt-skill assertion in loadSkillsDir.test.ts to the temp fixture skills root.
• Prevent globally/user-installed prompt skills from leaking into this test and making the expected skill-name list flaky.

Validation

• bun test src/skills/loadSkillsDir.test.ts

Notes

This is a tiny test-only cleanup from a fork. No runtime behavior changes.

[jatmn]

Findings

• [P2] Keep the isolated skill filter type-safe
  src/skills/loadSkillsDir.test.ts:37
  The new predicate dereferences optional skillRoot, and the combined predicate no longer leaves promptSkills narrowed to prompt commands for the later skillRoot assertions. bun x tsc --noEmit --pretty false now reports errors in this touched test file for skill.skillRoot possibly being undefined and for skillRoot not existing on non-prompt commands. Please guard skillRoot and keep the filtered array narrowed to prompt commands, for example with an explicit type predicate plus optional chaining.

[Vasanthdev2004]

Blockers

1. Type safety issue — The new predicate dereferences optional skillRoot without guarding, and the combined predicate doesn't leave promptSkills narrowed to prompt commands. This causes TypeScript errors in the touched test file.

Non-Blocking

• Tiny test-only cleanup (5 additions, 1 deletion).

Looks Good

• Addresses real test flakiness issue
• Prevents globally/user-installed prompt skills from leaking into test
• No runtime behavior changes

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Verdict: Changes Requested — type safety issue needs to be fixed.

[gnanam1990]

Confirmed @jatmn's point. The new isolated-skill predicate dereferences optional skillRoot and the combined predicate no longer narrows the array to prompt commands, so bun x tsc --noEmit reports the touched test file for skill.skillRoot possibly undefined and skillRoot missing on non-prompt commands. An explicit type-predicate that narrows to prompt commands plus optional chaining on skillRoot keeps it type-safe. Small change — happy to re-review as soon as it's green.