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/documentation/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: documentation
-description: Best practices for software documentation — README, API docs, ADRs, inline comments, changelogs, and knowledge base organization. Use when writing README files, designing documentation strategy, adding inline comments, or whenever the user mentions "documentation," "README," "ADR," "changelog," "docstring," "wiki," "documentation as code," or "docs."
+description: Best practices for software documentation — README, API docs, ADRs, inline comments, changelogs, and knowledge base organization. Use when writing README files, designing documentation strategy, adding inline comments. Detects from code context and project files — not dependent on specific language keywords."
 ---
 
 # Documentation Best Practices