fix: prevent reading SKILL.md files when listing available skills

[roomote]

Related GitHub Issue

Closes: #10393

Description

This PR attempts to address Issue #10393 where asking "list all skills" causes the model to read each SKILL.md file unnecessarily.

Root Cause:
The skills system prompt tells the model to read SKILL.md files when a skill applies, but it does not clearly distinguish between "using a skill" (which requires reading the full instructions) and "listing/describing skills" (which only needs the metadata already in the prompt).

Changes:

• Added a new <if_user_asks_to_list_skills> section to the skills system prompt in src/core/prompts/sections/skills.ts
• This section explicitly instructs the model to use ONLY the information already provided in <available_skills> (name, description, location) when users ask to list, show, display, or enumerate available skills
• Added corresponding test coverage

Feedback and guidance are welcome.

Test Procedure

1. Run the skills section tests:

   cd src && npx vitest run core/prompts/sections/__tests__/skills.spec.ts

2. All 3 tests pass, including the new test that verifies the <if_user_asks_to_list_skills> section is present in the generated prompt

Pre-Submission Checklist

• Issue Linked: This PR is linked to an approved GitHub Issue (see "Related GitHub Issue" above).
• Scope: My changes are focused on the linked issue (one major feature/fix per PR).
• Self-Review: I have performed a thorough self-review of my code.
• Testing: New and/or updated tests have been added to cover my changes (if applicable).
• Documentation Impact: I have considered if my changes require documentation updates (see "Documentation Updates" section below).
• Contribution Guidelines: I have read and agree to the Contributor Guidelines.

Documentation Updates

• No documentation updates are required.

Additional Notes

This is a prompt engineering fix that adds explicit instructions to prevent the model from unnecessarily reading SKILL.md files when users only want to know what skills are available.

[roomote]

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Review complete. No issues found.

This is a clean prompt engineering fix that adds explicit instructions to prevent the model from reading SKILL.md files when users ask to list available skills. The change is minimal, targeted, and all tests pass.

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