feat: make creator media edits render-safe (#3322)

* feat: make creator media edits render-safe

* fix: align media playback timing

* docs: add creator editing recipes

* docs: expand creator editing guidance

* fix: unify media source offsets

* fix: scale natural media duration

* fix: preserve natural media zero spans

* fix: align compiled natural media timing

* test: classify compiler media test as integration

* fix: drop inactive media windows

* fix: unify literal timing parsing

* fix: keep browser media parsing serializable

* fix: keep page timing readers strict

* fix: close remaining preview timing gaps

* fix(core): preserve Studio voice pitch at playback speed

* chore: keep creator contract source-neutral

skills/general-video/SKILL.md

@@ -59,6 +59,15 @@ Do not invent synonyms for these states. An ongoing “just build it” signal i
 - For `flow: automation`, choose the route and state it in one line in the first progress update.
 - For a specific edit, make the edit without inventing a new route.
 
+For a hard cut, trim, splice, or reorder of existing footage, duplicate the same
+video source into multiple clip elements. On each copy, set the source range
+with `data-media-start` plus `data-duration`, then set authored placement/order
+with `data-start`. Separately authored audio follows the identical clip ranges
+and timing on matching `<audio>` elements. `/hyperframes-core` owns this temporal
+edit; use `/hyperframes-keyframes` only for visual-property animation such as
+zoom, punch, pan, crop, mask, or `clip-path` on an inner wrapper.
+Copy the full contracts from `../hyperframes-core/references/creator-editing-recipes.md`.
+
 ### Companion flow
 
 When `flow: companion`: