fix: recursively copy entire skill directory during install

[Minitour]

Summary

• Bug: When installing a skill (local, GitHub, or GitLab), only \SKILL.md\ and top-level files were copied. Subdirectories and their contents were silently skipped.
• Fix: Made
  eadSkillFromDirectory\ recursively traverse subdirectories, collecting all files with their relative paths. The existing write logic already supports nested paths via \mkdirSync({ recursive: true }), so no changes were needed on the install side.
• Security checks (blocked phrases, character sanitization) continue to apply to all collected files.

Test plan

• Install a skill that has files in subdirectories (e.g.
  eferences/\ folder) from a local path and verify the entire directory tree is copied
• Install a skill from a GitHub repo with nested reference files and verify all files are present
• Install a skill with only \SKILL.md\ (no subdirectories) and verify it still works as before
• Verify security checks (blocked phrases) still apply to files in subdirectories

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