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/error-handling/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: error-handling
-description: Best practices for error handling across languages — exceptions, Result types, input validation, error boundaries, null safety, and observability. Use when designing error strategies, writing validation logic, handling API errors, or whenever the user mentions "error handling," "exception," "try-catch," "Result," "Option," "Either," "null check," "validation," "panic," or "error boundary."
+description: Best practices for error handling across languages — exceptions, Result types, input validation, error boundaries, null safety, and observability. Use when designing error strategies, writing validation logic, handling API errors. Detects from code context and project files — not dependent on specific language keywords."
 ---
 
 # Error Handling