Replaces the broken/fragmented preview with a single surface that renders a
DRAFT playlist exactly as a device does, by reusing the player's renderer in a
same-origin iframe. Fixes "not all items load" (one renderer, full type union)
and inherits the player's YouTube correctness (YT.Player handshake).
Server:
- deviceSocket: extract assemblePayload() (zone-reset + canonical shape) from
buildPlaylistPayload so the device path and preview can't drift. Pure refactor
(all 149 tests green).
- playlists: GET /:id/preview-payload (requirePlaylistRead, workspace-scoped).
Draft-aware via buildSnapshotItems (live items, not published_snapshot);
derivePreviewLayout() resolves layout from the playlist's own zone-bound items
(0 zoned -> fullscreen; 1 -> use it; >1 -> dominant + ambiguous flag, never
crashes). orientation validated/passthrough; wall_config/timezone null.
Player (renderer UNTOUCHED):
- ?preview=1&playlist=ID boot branch: fetch preview-payload (same-origin Bearer
token) and call handlePlaylistUpdate(). Gated before the pairing/socket path
so the unpaired auto-connect never fires. All socket emits already guarded.
- Webpage widgets: always-visible honest note (no auto-detection — an XFO
refusal is provably indistinguishable client-side from a working embed).
Dashboard:
- playlists: Preview button + player-iframe modal with landscape/portrait toggle.
- widgets: same honest note on the existing widget preview modal (the surface the
bug was reported on).
- i18n x6 (en/es/fr/de/it/pt) + player i18n x5.
Validated end-to-end (headless Chrome + CDP): preview boots, webpage note
renders, 3-zone layout derives+renders, shape parity with device snapshot proven
on real data, auth gate returns 401. The world-readable /uploads finding is
tracked separately as #107 (not a #104 concern — same path the device uses).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
