[dazzatronus]

Before the first tween the preview ramped from the neutral value, so a delayed fade-in previewed as a fade-out followed by a fade-in. The render holds the first tween's from. Gaps between tweens were always linear in the preview, while the render takes the next tween's interpolation. KeyframeBuilder is now a point model like the render's, so both behaviours follow from it. Video speed keeps linear gaps, because the render handles speed on its own path.

Risk: out-only reveals and wipes no longer ramp across the whole clip.

Verify: npm test (2354, +5, two obsolete tests removed).

#	PR	Adds	Why separate
1/10	#249	Internal type for the render's default curve	Mechanical, no behaviour change
2/10	#250	Transitions match the render	Transition presets
3/10	#251	shuffle* previews	A missing preset
4/10	#252	Slide effects match the render	Effect presets
5/10	#253	Keyframes hold and ease like the render	Keyframe model
6/10	#254	Presets compose over keyframes	Builds on 2–5
7/10	#255	The toolbar allows presets with keyframes	UI change that needs 6/10
8/10	#256	Default fps matches the render	Output settings
9/10	#257	shotstack-canvas 2.14.1	Dependency bump
10/10	#258	html5 capture sees the page's markup	Uses 9/10's new inputs

Merge bottom-up, retargeting each PR after its predecessor lands. Since #248 the release workflow skips the release when the merged PR's title starts [n/m] with n < m, so 1/10 to 9/10 hold, and 10/10 releases the stack as one version.

Merge subject: [5/10] fix: hold the first keyframe value and ease gaps like the render. The repo squashes a single-commit PR under its commit message, so type this in the merge dialog.

[github-actions]

🎉 This PR is included in version 2.29.2 🎉

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• GitHub release

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