feat(packages): add slider core layer

[mihar-22]

ref: #275, #267, #269

Summary

Add the runtime-agnostic core layer for the slider component system — SliderCore, TimeSliderCore, and VolumeSliderCore — plus supporting utilities. This is the foundation that both React and HTML slider components will build on.

Changes

• @videojs/utils: Add clamp and roundToStep (/number subpath), rafThrottle, isRTL, and fix formatTimeAsPhrase(0) returning empty string
• @videojs/core: Add SliderCore (generic slider state + ARIA), TimeSliderCore (seek slider with buffer tracking), VolumeSliderCore (volume 0-1 → 0-100 mapping, muted fill)
• Constants: SliderDataAttrs, TimeSliderDataAttrs, SliderCSSVars for data attributes and CSS custom properties
• Time slider drag precision: Uses raw sub-second values during drag for smooth scrubbing on mobile/short videos; step snapping only applies to keyboard

Implementation details

• Domain cores (TimeSliderCore, VolumeSliderCore) use canonical media state types directly (MediaTimeState & MediaBufferState, MediaVolumeState) with Pick<> on state interfaces — no wrapper types
• Domain cores have their own getTimeState(media, interaction) / getVolumeState(media, interaction) rather than overriding base getState (incompatible signatures)
• interactive = dragging || pointing || focused
• bufferedEnd computed internally from media.buffered ranges
• Design doc and implementation plan updated to reflect all decisions made during implementation

Testing

pnpm -F @videojs/utils test   # 187 tests
pnpm -F @videojs/core test    # 269 tests
pnpm typecheck                # clean

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Project	Deployment	Actions	Updated (UTC)
vjs-10-demo-react	Ignored		Feb 13, 2026 2:28pm

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📦 Bundle Size Report

Package	Size	Diff		%
@videojs/core	5.37 kB	+804 B	████████	+17.1%	🔴
@videojs/element	1.60 kB	0 B	░░░░░░░░	0%	✅
@videojs/html	8.64 kB	+744 B	████░░░░	+9.2%	🔺
@videojs/react	7.75 kB	+738 B	█████░░░	+10.3%	🔴
@videojs/store	1.94 kB	0 B	░░░░░░░░	0%	✅
@videojs/utils	2.18 kB	+302 B	███████░	+15.6%	🔴

Total: 27.49 kB · +2.53 kB · +10.1%

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Entry Breakdown

Subpath sizes are the additional bytes on top of the root entry point, measured by bundling root + subpath together and subtracting the root-only size.

@videojs/core

Entry	Base	PR	Diff	%
.	1.97 kB	2.77 kB	+820 B	+40.6%	🔴
./dom	2.61 kB	2.60 kB	-16 B	-0.6%	🔽
total	4.59 kB	5.37 kB	+804 B	+17.1%

@videojs/element

Entry	Base	PR	Diff	%
.	817 B	817 B	0 B	0%	✅
./context	823 B	823 B	0 B	0%	✅
total	1.60 kB	1.60 kB	0 B	0%

@videojs/store

Entry	Base	PR	Diff	%
.	1.29 kB	1.29 kB	0 B	0%	✅
./html	468 B	468 B	0 B	0%	✅
./react	199 B	199 B	0 B	0%	✅
total	1.94 kB	1.94 kB	0 B	0%

@videojs/utils

Entry	Base	PR	Diff	%
./array	104 B	104 B	0 B	0%	✅
./dom	553 B	684 B	+131 B	+23.7%	🔴
./events	227 B	227 B	0 B	0%	✅
./function	197 B	197 B	0 B	0%	✅
./object	119 B	119 B	0 B	0%	✅
./predicate	265 B	265 B	0 B	0%	✅
./time	465 B	478 B	+13 B	+2.8%	🔺
./number	—	158 B	—		🆕
total	1.88 kB	2.18 kB	+302 B	+15.6%

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ℹ️ How to interpret

Sizes are minified + brotli, measured with esbuild.
Package totals are computed as root size + marginal subpath costs.
Subpath marginal cost = (root + subpath bundled together) − root alone.

Icon	Meaning
✅	No change
🔺	Increased ≤ 10%
🔴	Increased > 10%
🔽	Decreased
🆕	New (no baseline)

Run pnpm size locally to check current sizes.