Skill auto-router via UserPromptSubmit hook
Routing pattern: a `UserPromptSubmit` hook (configured in `~/.claude/settings.json`) intercepts every user prompt BEFORE Claude analyzes the natural triggers of skills. The hook runs a bash/python script that regexes the prompt, `(research|investigate|explore)` loads the researcher skill, `(tdd|test first)` loads the tdd skill, etc. The target skill is written to a transient file Claude reads on the next turn. Zero-token routing, 100% predictable.