fix: silently skip /denied/ and other non-hosted download prefixes

These are valid entries we've been asked not to host — no need to
log warnings for them.

claude-opus-4-6@MacFiver

bin/update-software-hashes.mjs

@@ -336,10 +336,13 @@ async function main() {
     try {
       const localZip = toLocalPath(fileLink);
       if (!localZip) {
-        logWarn(`  [${id}] Unsupported file_link prefix: ${fileLink}`);
-        errors++;
+        // /denied/ and other non-hosted prefixes — skip silently
+        skipped++;
         processed++;
         currentState.lastProcessedId = id;
+        if (processed % 500 === 0) {
+          await checkpoint();
+        }
         continue;
       }