fix(three-dissolve): set __hf fallback in outer catch for CDN failures

If CDN scripts fail to load (THREE undefined), the outer catch fires
but never set window.__hf — the engine polls for it forever until
the 120s CI timeout. Provide a no-op fallback so the engine sees
readiness even on total init failure.

Author: miguel-heygen

registry/blocks/three-dissolve/three-dissolve.html

@@ -947,6 +947,7 @@
           renderAt(window.__hfThreeTime || 0);
         } catch (error) {
           console.error("three-dissolve init error:", error);
+          if (!window.__hf) window.__hf = { duration: 8, seek: function () {} };
           resolveReady();
         }
       })();