fix: harden Roblox API dump sync to skip missing builds

The sync step was using latest.json to resolve the build GUID, but the
latest build's files are often missing from the archive. curl without
--fail silently wrote the 404 response body as the dump, corrupting it.

Now uses metadata.json to find the latest GUID that actually has
Full-API-Dump.json available, adds curl -f, and validates JSON output.
Also restores the dump from the last available build.

Author: jrmelsha

.github/workflows/sync-sources.yml

@@ -55,13 +55,27 @@ jobs:
 
       - name: Sync Roblox API dump
         run: |
-          echo "Resolving latest build GUID..."
-          GUID=$(curl -s "https://raw.githubusercontent.com/RobloxAPI/build-archive/master/data/production/latest.json" | jq -r '.GUID')
+          BASE="https://raw.githubusercontent.com/RobloxAPI/build-archive/master/data/production"
+
+          echo "Resolving latest build GUID with Full-API-Dump.json available..."
+          GUID=$(curl -sf "$BASE/metadata.json" | jq -r '
+            [.Missing // {} | to_entries[] | select(.value | index("Full-API-Dump.json")) | .key] as $missing |
+            [.Builds[] | select(.GUID as $g | $missing | index($g) | not)] | last | .GUID
+          ')
+
+          if [ -z "$GUID" ] || [ "$GUID" = "null" ]; then
+            echo "::error::Failed to resolve a valid build GUID from metadata.json"
+            exit 1
+          fi
           echo "GUID: $GUID"
 
           mkdir -p roblox-api
-          curl -sL "https://raw.githubusercontent.com/RobloxAPI/build-archive/master/data/production/builds/$GUID/Full-API-Dump.json" \
-            -o roblox-api/Full-API-Dump.json
+          curl -sfL "$BASE/builds/$GUID/Full-API-Dump.json" -o roblox-api/Full-API-Dump.json
+
+          if ! jq empty roblox-api/Full-API-Dump.json 2>/dev/null; then
+            echo "::error::Downloaded Full-API-Dump.json is not valid JSON"
+            exit 1
+          fi
           echo "Done: roblox-api/Full-API-Dump.json"
 
       - name: Commit and push