fix(skills): avoid mislabeling local skills as builtin in skills list

[arceus77-7]

What does this PR do?

Fixes incorrect source labeling in hermes skills list.

Previously, every non-hub-installed skill was shown as builtin. This misclassified user-managed skills (for example skills synced in from external managers) as built-in Hermes skills.

This PR classifies installed skills into:

• hub (present in Hub lockfile)
• builtin (present in bundled skills manifest)
• local (everything else under ~/.hermes/skills/)

It also adds a --source local filter.

Related Issue

Fixes #861

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✅ Tests (adding or improving test coverage)

Changes Made

• Updated source classification in hermes_cli/skills_hub.py (do_list):
  • Reads bundled skill names from tools.skills_sync._read_manifest().
  • Distinguishes hub, builtin, and local skills.
  • Updates summary counts to include local skills.
• Updated /skills help text to document --source hub|builtin|local.
• Updated CLI argument choices in hermes_cli/main.py to include local.
• Added tests in tests/hermes_cli/test_skills_hub.py:
  • test_do_list_distinguishes_hub_builtin_and_local
  • test_do_list_local_filter

How to Test

1. Run tests:
   • ./venv/bin/pytest tests/hermes_cli/test_skills_hub.py -q
2. Add or ensure a non-bundled local skill exists under ~/.hermes/skills/.
3. Run:
   • hermes skills list
   • hermes skills list --source local
4. Verify local skill shows Source=local and no longer appears as builtin.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS

Documentation & Housekeeping

• N/A for this scoped bugfix: README/docs/config/AGENTS/tool-schema updates
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide

Screenshots / Logs

• ./venv/bin/pytest tests/hermes_cli/test_skills_hub.py -q -> 3 passed
• Note: full pytest tests/ -q was not run for this focused fix.