my-sea spectate: live spread-sync + owner seat-ring push + visit caption fix — TDD

Three fixes to the my-sea spectator (bud-sea), all flowing over the existing
`mysea_<owner>` spectate consumer:

VISIT CAPTIONS (.sea-pos-label) — two bugs left every CROWN/COVER/… caption
blank on my_sea_visit:
- empty-hand: `label_by_position` was built from `latest_draw_slots`, which
  returns [] when the owner's hand is empty (only a significator placed) — so
  an owner mid-setup showed no captions, while her OWN my_sea (whose JS seeds
  labels from the POSITION_LABELS constant) showed them. Now the view pulls
  captions straight from POSITION_LABELS[spread], drawn-cards-independent.
- `--seciUser` typo (used once, never defined) → invalid colour dropped → the
  labels inherited the body colour, contrasting on some palettes but blending
  into the felt on others (read as "missing"). → `--secUser`.

SPREAD-SYNC — the owner's live draw pushed only the hand, not the spread, so a
post-DEL spread switch landed the new cards into the OLD spread's cells (the
asymmetry the user hit: owner on desire-obstacle-solution, visitor still laid
out as escape-velocity). The spread now rides each `sea_draw` broadcast;
`_applySpread` re-sets `data-spread` (CSS keys cell visibility off it),
re-captions from a server-sourced POSITION_LABELS json_script, + clears stale
fills before `_applyHand` repopulates against the right layout.

OWNER-SIDE LIVE SEAT PUSH — the owner's my_sea now subscribes to her own
spectate WS for `sea_seats`, so visitors arriving (deposit → 2C-6C) / leaving
(BYE) appear without a refresh, same broadcast the spectators get. The visit
page's inline `_renderSeats` is hoisted into my-sea-seats.js as the shared
`mySeaRenderSeats(seats, myToken)` (+ `mySeaConnectSeatRing`); each page passes
its own self-token (owner page passes '' — her 1C isn't --self server-side).

Coverage:
- ITs: MySeaVisitEmptyHandLabelsTest (captions present + rendered for an empty
  hand); MySeaLockHandViewTest broadcast test asserts the spread arg; spectate
  consumer test asserts the hand+spread relay (channels).
- Jasmine: 6 new MySeaSeatsSpec cases for mySeaRenderSeats (per-seat rebuild,
  --self by token, owner-page no-self, no-duplicate re-render, one-shot flare).
- Live-verified in Firefox: captions paint khaki on the brown palette; a
  desire-obstacle-solution sync flips data-spread + relabels Solution/Obstacle/
  Desire + hides leave/cover/lay.

[[feedback-jsonfield-exclude-sqlite-null]] not implicated; spread map is a plain
dict lookup. 304 gameboard ITs + Jasmine green.

Code architected by Disco DeDisco <discodedisco@outlook.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/static_src/scss/_gameboard.scss

@@ -432,7 +432,7 @@ body.page-gameboard {
     text-transform: uppercase;
     font-weight: 600;
     opacity: 1;
-    color: rgba(var(--seciUser), 1);
+    color: rgba(var(--secUser), 1);
     text-shadow: 0 0 0.25rem rgba(var(--priUser), 1);
     text-align: center;
     pointer-events: none;