feat(manifests): Update manifests and validator for Phase 12 plugin types

[rogermt]

Summary

Update all plugin manifests for Phase 12 plugin type enforcement.

Changes

• OCR manifest: remove mode, add type: ocr, tool name -> id + title
• YOLO manifest: remove mode, add type: yolo, all 4 tools name -> id + title
• plugin_template manifest: created with type: custom
• validate_manifest.py: updated to validate type instead of mode

Testing

• Pre-commit hooks pass (validate-yolo-manifest, enforce-plugin-structure)

Checklist

• Ruff lint clean
• Mypy type check clean
• Manifest validation passes