fix(skills): distinguish external skill install paths and open real location

[vcfgv]

Summary

Fixes a path mismatch in Skills:

• Skills list could show items discovered from non-managed locations
• But "Open Folder"/README lookup still assumed ~/.openclaw/skills

This caused "visible but cannot open" behavior, especially on Windows or when skills were installed via external clawhub flows.

- `source`, `baseDir`, `filePath` in skills state model

• Prefer Gateway skills.status path fields when available
• Extended ClawHub list result to include managed location metadata
• Added new host API route:
  • POST /api/clawhub/open-path to open the actual skill directory
• Updated README open logic:
  • open-readme now accepts and prefers baseDir when provided
• Skills UI updates:
  • Show source badge + resolved path in list and detail
  • Add "Open Actual Folder" action per-skill
  • Add "Copy path" action
  • Keep global "Open Skills Folder" behavior unchanged (managed dir)
• i18n updates (en/zh/ja) for new labels/toasts
• README updates (en/zh/ja) to document multi-source discovery and actual path visibility

Why

Align display/discovery and folder-open behavior to the same source-of-truth so users can reliably locate externally installed skills.

Validation

• Targeted test passed:
  • npm test -- tests/unit/skills-errors.test.ts
• npm run typecheck still reports an existing unrelated baseline issue in this environment:
  • src/hooks/use-stick-to-bottom-instant.ts missing module use-stick-to-bottom
• Full test suite still has pre-existing unrelated failures (localStorage/test env), not introduced by this change.