feat(producer): auto-fallback screenshot capture for raf and iframes (#331)

* fix(core): drive adapter seeks when composition has no GSAP timeline

renderSeek returned early when deps.getTimeline() was null, skipping the
onDeterministicSeek call that drives all frame adapters (CSS, WAAPI,
Lottie, Three.js). That meant compositions using any non-GSAP animation
primitive froze on their initial frame during capture.

Now we still quantize the seek time and fire onDeterministicSeek even
without a timeline, so each adapter gets a chance to advance.

GSAP compositions are unaffected — timeline-driven seek still takes the
same path it did before.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* feat(producer): auto-fallback screenshot capture for raf and iframes

Co-Authored-By: Codex <codex@openai.com>

* test(producer): add render compatibility regression fixtures

Co-Authored-By: Codex <codex@openai.com>

* fix(core): scrub CSS animations via WAAPI currentTime

Co-Authored-By: Codex <codex@openai.com>

* test(producer): cover css keyframe renders

Co-Authored-By: Codex <codex@openai.com>

* fix(producer): propagate virtual time into iframe documents

Co-Authored-By: Codex <codex@openai.com>

* test(producer): refresh iframe docker golden

Co-Authored-By: Codex <codex@openai.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: Codex <codex@openai.com>

.github/workflows/regression.yml

@@ -35,7 +35,9 @@ jobs:
       matrix:
         include:
           - shard: fast
-            args: "--sequential --exclude-tags slow"
+            args: "--sequential --exclude-tags slow,render-compat"
+          - shard: render-compat
+            args: "--sequential gsap-letters-render-compat css-spinner-render-compat raf-ball-render-compat iframe-render-compat"
           - shard: styles-a
             args: "style-1-prod style-2-prod style-3-prod"
           - shard: styles-b