feat(hub-guide): language-agnostic auto-trigger across all skills

- Add principle 27: 'Language-Agnostic Auto-Trigger' to engineering-principles
- Remove hardcoded English-only keyword lists from all 26 skill descriptions
- Replace with concept-based detection: triggers from code context, project files,
  and file types regardless of spoken language
- Update detect-project.sh hook output with language-agnostic message

skills/python/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: python
-description: Python best practices — typing, project structure, packaging, FastAPI patterns, async, testing, and idiomatic Python. Use when writing Python code, structuring a Python project, or whenever the user mentions "Python," "FastAPI," "Django," "pytest," "PEP 8," "type hints," "Pydantic," "asyncio," "pip," "poetry," or "uv."
+description: Python best practices — typing, project structure, packaging, FastAPI patterns, async, testing, and idiomatic Python. Use when writing Python code, structuring a Python project. Triggers when working with this language's files, regardless of spoken language."
 ---
 
 # Python Best Practices