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/go/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: go
-description: Go best practices — idiomatic Go, project layout, error handling, interfaces, concurrency, testing, and dependency management. Use when writing Go code, reviewing Go projects, or whenever the user mentions "Go," "Golang," "goroutine," "channel," "interface," "defer," "go mod," "gRPC," "net/http," "chi," "echo," "fiber," or "go test."
+description: Go best practices — idiomatic Go, project layout, error handling, interfaces, concurrency, testing, and dependency management. Use when writing Go code, reviewing Go projects. Triggers when working with this language's files, regardless of spoken language."
 ---
 
 # Go Best Practices