Redesign README with hero banner, feature grid, collapsibles

Replaces the plain doc-style README with the design from the handoff:

- assets/banner.svg — cyberpunk hero (HA blue × neon pink, scanlines,
  pixel halo, scanning eye, feature chips, live-status strip)
- README — tagline with punch, "Why this exists" 3-column intro,
  feature highlights as 2×4 grid, cleaner architecture diagram with
  output side (TTS / lights / notify) visible, long sections (modes,
  spoiler, voice, capture CLI, entities, services, troubleshooting)
  moved into <details> collapsibles, AI backends + models as tables,
  games split into video / card+tabletop columns, footer brand strip

Pure docs/marketing change — no integration code touched.

https://claude.ai/code/session_013unZ2jW6ojs2LLWfTPREhu

Author: claude