Resolve manifest via the mystic reference only

Drop the hardcoded MANIFEST_TX_ID fallback from the app, the deploy script
and the metadata prerender. The mystic reference now points at the manifest
that includes arweave-for-ao, so the UI picks up new ships without a code
change.

scripts/deploy.mjs

@@ -223,12 +223,6 @@ async function createUploader(uploadMode, arweave, jwk) {
   };
 }
 
-async function resolveBlogManifestTxId() {
-  const source = await fs.readFile(sourceConfigPath, "utf8");
-  const match = source.match(/MANIFEST_TX_ID\s*=\s*"([^"]+)"/);
-  return match?.[1] || "";
-}
-
 async function resolveBlogManifestReferenceName() {
   const source = await fs.readFile(sourceConfigPath, "utf8");
   const match = source.match(/MANIFEST_REFERENCE_NAME\s*=\s*"([^"]+)"/);
@@ -344,8 +338,7 @@ async function fetchPostSlugs(gateway, blogManifestTxId) {
 async function resolvePostSlugs(gateway) {
   const candidates = [
     await getLatestManifestFromReference(gateway),
-    await getLatestManifestFromAo(),
-    await resolveBlogManifestTxId()
+    await getLatestManifestFromAo()
   ].filter(Boolean);
 
   for (const blogManifestTxId of candidates) {