One-time researcher onboarding interview that compiles a `taste/` corpus (SOUL.md, STYLE.md, METHODOLOGY.md, DISMISSALS.md, MEMORY.md, INDEX.md) capturing the researcher's intellectual taste, beliefs, and values. Auto-injects INDEX.md into every future session via SessionStart. Triggers on first install ("no taste corpus found"), explicit `/onboard`, `/onboard --deep` for Tier 2 voice laddering, or `/onboard --redo` / `/onboard --section <name>` to refresh.
