fix(build): a failed agents-digest regen fails gen-skill-docs instead of deferring the red to CI

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/gen-skill-docs.ts

@@ -1158,6 +1158,9 @@ if (!DRY_RUN) {
     } catch (err) {
       const msg = err instanceof Error ? err.message : String(err);
       console.error(`[gen-agents-digest] FAILED: ${msg}`);
+      // The digest is a committed freshness-gated artifact: a local build
+      // that silently ships it stale defers the red to CI. Fail the build.
+      process.exitCode = 1;
     }
   })();
 }