fix(deploy): route /dict through caddy to the gateway (local eval)

The edge caddy @gateway matcher was missing /dict/*, so the client's dictionary
fetch fell to the static landing catch-all: it received a non-dawg blob (200 OK),
which the reader parsed into a bogus finder that reports every word missing — a
valid first move showed as illegal with no network fallback. Add /dict/* to the
gateway route.

Hardening + the cross-test that would have caught it:
- reader: reject a blob whose 32-bit size header != its byte length, so a
  non-dawg page or a truncated download now throws and the loader falls back to
  the network preview instead of silently validating against garbage.
- eval.parity: an adapter conformance suite that drives evaluateLocal through the
  real letter-space path (the server alphabet table, a letter board and letter
  placements) against the engine — the algorithm-level validate.parity did not
  exercise the adapter. validategen now emits the alphabet table for it.
- a CI deploy probe asserts {edge}/dict reaches the gateway (401), not the landing.
- the DebugPanel reports the feature flag, the bad-connection breaker and the
  cached dictionaries with their sizes; its reset also clears the dict cache.

.gitea/workflows/ci.yaml

@@ -395,6 +395,23 @@ jobs:
           docker logs --tail 50 scrabble-backend || true
           exit 1
 
+      - name: Probe the /dict edge route reaches the gateway
+        run: |
+          set -u
+          # The client fetches each game's dictionary blob at {edge}/dict/{variant}/{version}
+          # for the local move preview. If caddy does not route /dict to the gateway the request
+          # falls to the static landing and the client silently gets a non-dawg blob. Probed
+          # unauthenticated it must be the gateway's 401 (the route reaches the gateway), never a
+          # 404/200 from the landing catch-all.
+          out="$(docker run --rm --network edge alpine:3.20 wget -S -q -O /dev/null http://scrabble/dict/scrabble_en/v1 2>&1 || true)"
+          echo "$out" | grep -E "HTTP/" || true
+          if echo "$out" | grep -q " 401"; then
+            echo "ok: /dict reaches the gateway (401 unauthenticated)"
+          else
+            echo "FAIL: /dict did not reach the gateway (expected 401) — caddy route missing?"
+            exit 1
+          fi
+
       - name: Probe the Telegram validator and bot liveness
         run: |
           set -u