sync-status: dRPC-homogeneous block-lag status + fix never-used reference fallbacks

Match the dRPC gateway's per-chain "how many blocks behind is ok" model instead of a
fixed 2s/5s timestamp tolerance:
- check-health.sh: compare the reference head vs local head by BLOCK NUMBER and classify
  with the chain's dRPC lag thresholds (LAGGING_LAG/SYNCING_LAG, in blocks, from
  chains.yaml). dRPC uses the two thresholds inconsistently across chains (sometimes
  lagging<syncing, sometimes the reverse) so the smaller is the online boundary and the
  larger the syncing/drop boundary. Defaults 2/6 when a chain has no thresholds.
- multicurl.sh: also skip responses with result:null (a lagging endpoint lacking the
  requested block) so the fallback reference URLs are actually tried. Previously the first
  endpoint's {"result":null} was accepted as success -> fallbacks never ran, and the null
  reference hash made check-health report false "forked" (the online/forked flapping).
- sync-status.sh: resolve the lag thresholds (by drpc slug or chain id) and export
  LAGGING_LAG/SYNCING_LAG.
- reference-rpc-endpoint.sh: add --lags and --block-time-ms lookups.
- reference-rpc-endpoint.json: regenerated with per-chain block_time_ms + lagging_lag +
  syncing_lag (additive).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

reference-rpc-endpoint.sh

@@ -44,6 +44,51 @@ if [ "$1" = "--protocol" ]; then
     exit 0
 fi
 
+# Look up the expected block time (milliseconds) for a registry key (drpc slug) or chain id.
+# Used by sync-status.sh / check-health.sh to scale the lag thresholds per chain.
+if [ "$1" = "--block-time-ms" ]; then
+    if [ $# -lt 2 ]; then
+        echo "Usage: $0 --block-time-ms <slug|chainid>"
+        exit 1
+    fi
+    key="$2"
+    # Try by slug first
+    bt=$(jq -r --arg k "$key" '.[$k].block_time_ms // empty' "$json_file" 2>/dev/null)
+    if [ -z "$bt" ]; then
+        # Fall back to lookup by chain id (decimal; convert hex)
+        idk="$key"
+        [[ "$idk" == 0x* ]] && idk=$(printf "%d" "$idk" 2>/dev/null)
+        if [[ "$idk" =~ ^[0-9]+$ ]]; then
+            bt=$(jq -r --arg id "$idk" 'first(.[] | select(.id == ($id | tonumber)) | .block_time_ms) // empty' "$json_file" 2>/dev/null)
+        fi
+    fi
+    [ -z "$bt" ] && exit 1
+    echo "$bt"
+    exit 0
+fi
+
+# Look up the dRPC lag thresholds (in BLOCKS) for a registry key (slug) or chain id.
+# Prints "<lagging_lag> <syncing_lag>". Used by sync-status.sh -> check-health.sh so our
+# online/lagging/syncing status matches the dRPC gateway's per-chain lag model.
+if [ "$1" = "--lags" ]; then
+    if [ $# -lt 2 ]; then
+        echo "Usage: $0 --lags <slug|chainid>"
+        exit 1
+    fi
+    key="$2"
+    lags=$(jq -r --arg k "$key" 'if (.[$k].lagging_lag != null and .[$k].syncing_lag != null) then "\(.[$k].lagging_lag) \(.[$k].syncing_lag)" else empty end' "$json_file" 2>/dev/null)
+    if [ -z "$lags" ]; then
+        idk="$key"
+        [[ "$idk" == 0x* ]] && idk=$(printf "%d" "$idk" 2>/dev/null)
+        if [[ "$idk" =~ ^[0-9]+$ ]]; then
+            lags=$(jq -r --arg id "$idk" 'first(.[] | select(.id == ($id | tonumber)) | select(.lagging_lag != null and .syncing_lag != null) | "\(.lagging_lag) \(.syncing_lag)") // empty' "$json_file" 2>/dev/null)
+        fi
+    fi
+    [ -z "$lags" ] && exit 1
+    echo "$lags"
+    exit 0
+fi
+
 # Look up by rollup_version (for Aztec: version from result.header.globalVariables.version)
 if [ "$1" = "--rollup-version" ]; then
     if [ $# -lt 2 ]; then