Replaces the T20 stub. L1 dashboard renders greeting, "Describe the
problem" intake card (autofocus textarea, optional customer fields,
primary "Start walk" CTA), open-tickets queue (Phase 1: display-only),
and a "Resume in progress" widget listing the L1's active sessions
ordered by last_step_at DESC. Empty-state card shows on accounts with
no queue + no active sessions (first-run nudge to upload KB or auth flows).
Adds /api/l1.ts (full L1 API client surface) and /types/l1.ts.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
