Merge upstream/main into pr/mapillary-layer

Brings in #744 (share-link token ledger). package.json: keep the branch's
sorted scripts and add layer-token:next and layer-token:check.

Street Level's token moves from the provisional `3` to `0`: following
CONTRIBUTING, the provisional entry was removed and
`npm run layer-token:next -- street-level` assigned `0` (free digits in
order). It is added to the registry and to
src/data/layerStateTokenReservations.json, and
`npm run layer-token:check -- --base-ref upstream/main` passes (28
published, 1 new). No link with the provisional token was ever published.

Pinned token tests move with the ledger as CONTRIBUTING asks: 29
reservations, next free digit `3`, and the competing-PR and retired-digit
scenarios shift up one free digit (0->3, 3->4) so they still test the same
rules. The README share examples and the free-digit notes in
CONTRIBUTING and CURRENT-STATE now read `0`.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

scripts/format-scope.json

@@ -4,6 +4,11 @@
   "scripts/format-scope.json",
   "scripts/package-boundaries.json",
   "scripts/format.mjs",
+  "scripts/next-layer-state-token.mjs",
+  "scripts/check-layer-state-tokens.mjs",
+  "scripts/qa-layer-token-twochar.mjs",
+  "src/data/layerStateTokenReservations.json",
+  "src/data/layerStateTokenLedger.test.mjs",
   "scripts/check-package-boundaries.mjs",
   "scripts/precompute-cctv-heights.mjs",
   "src/tooling/precomputeCctvHeights.test.mjs",