fix(build): clarify generated-file check hint and drop redundant catalog step (#998)

The shared stale-file hint told developers to commit regenerated output, which is wrong for the gitignored build catalog. mcp-catalog:generate no longer re-runs the generator after build:cached since build:unlocked already produces it.

scripts/lib/generated-file.mjs

@@ -33,7 +33,7 @@ export const ensureGeneratedFile = async ({
     return { changed: false };
   if (check)
     throw new Error(
-      `${path} is missing or stale. Run \`${generateCommand}\` and commit the result.`,
+      `${path} is missing or stale. Run \`${generateCommand}\` to regenerate it; commit the result if the file is tracked.`,
     );
   await writeFile(path, preserveLineEndings(source, existing), "utf8");
   return { changed: true };