fix: regression fixes — conditional rebind + updated compilation baselines

1. Only call __hfForceTimelineRebind() when the timeline poll actually
   had to wait (pollDuration > 2 intervals). For compositions with
   synchronous timeline registration, the rebind was unnecessary and
   shifted render timing, causing PSNR regressions in chat and
   gsap-letters-render-compat.

2. Regenerate compiled.html baselines for missing-host-comp-id and
   overlay-montage-prod to match the new flattenInnerRoot behavior
   (data-composition-id stripped from inlined inner roots, replaced
   with data-hf-authored-id).

3. Add late-bind polling to runtime init.ts — after external
   compositions load, poll for 5s to detect async timelines that
   register after initial binding (e.g. from fetch callbacks).

packages/core/src/runtime/init.ts

@@ -1469,6 +1469,33 @@ export function initSandboxRuntimeModular(): void {
         applyCaptionOverrides();
         postTimeline();
         postState(true);
+
+        let lateBindChecks = 0;
+        const lateBindInterval = setInterval(() => {
+          if (++lateBindChecks > 50) {
+            clearInterval(lateBindInterval);
+            return;
+          }
+          const hosts = document.querySelectorAll("[data-composition-id]");
+          let allBound = true;
+          for (let i = 0; i < hosts.length; i++) {
+            const id = hosts[i].getAttribute("data-composition-id");
+            if (id && !timelines[id]) {
+              allBound = false;
+              break;
+            }
+          }
+          if (allBound && lateBindChecks > 1) {
+            clearInterval(lateBindInterval);
+            return;
+          }
+          if (!allBound) return;
+          childrenBound = false;
+          bindRootTimelineIfAvailable();
+          postTimeline();
+          postState(true);
+          clearInterval(lateBindInterval);
+        }, 100);
       });
   } else {
     // No external/inline compositions to load — apply caption overrides immediately