README: update episode count to 30; note dropped 2026-05-11 episodes

Drop 2026-05-11/episode_{000,002} (no-contact test recordings)

Add tasks.json registry; README per-task configs and task-first schema

Restructure to task-first layout: <task>/<date>/episode_*

Add dataset card with schema, quick start, caveats, and roadmap

Add processed mode1_v1 / 2026-05-11 (17 episodes)

Add processed dataset (mode1_v1: 2026-03-23 + 2026-05-10)

initial commit