feat(skin): add audio skins for HTML and React presets (#772)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/skins/src/shared/audio-icon-state.css

@@ -0,0 +1,37 @@
+/* ==========================================================================
+   Icon State Visibility for Audio Skins
+
+   Data-attribute-driven visibility rules for multi-state icon buttons.
+   Uses :is() with both element selectors (for HTML custom element wrappers)
+   and class selectors (for React rendered SVG elements).
+   ========================================================================== */
+
+/* --- All icons hidden by default --- */
+
+.media-button--play .media-icon--restart,
+.media-button--play .media-icon--play,
+.media-button--play .media-icon--pause,
+.media-button--mute .media-icon--volume-off,
+.media-button--mute .media-icon--volume-low,
+.media-button--mute .media-icon--volume-high {
+  display: none;
+  opacity: 0;
+}
+
+/* --- Active icon per state --- */
+
+/* Play: ended → restart */
+.media-button--play[data-ended] .media-icon--restart,
+/* Play: paused (not ended) → play */
+.media-button--play:not([data-ended])[data-paused] .media-icon--play,
+/* Play: playing (not paused, not ended) → pause */
+.media-button--play:not([data-paused]):not([data-ended]) .media-icon--pause,
+/* Mute: muted → volume off */
+.media-button--mute[data-muted] .media-icon--volume-off,
+/* Mute: volume low (not muted) → volume low */
+.media-button--mute:not([data-muted])[data-volume-level="low"] .media-icon--volume-low,
+/* Mute: volume high (not muted, not low) → volume high */
+.media-button--mute:not([data-muted]):not([data-volume-level="low"]) .media-icon--volume-high {
+  display: block;
+  opacity: 1;
+}

packages/skins/src/shared/native-captions.css

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+/* ==========================================================================
+   Native Caption Bridge
+   ---------------------------------------------------------------------------
+   Receives CSS custom properties set by any skin and applies them to the
+   native WebKit text track container on the slotted <video> element.
+
+   This stylesheet MUST live in the light DOM because ::slotted() cannot be
+   chained with vendor pseudo-elements like ::-webkit-media-text-track-container.
+
+   CSS custom properties cascade through the shadow DOM boundary, so skins
+   define the values and this bridge reads them.
+   ========================================================================== */
+
+.media-skin > video::-webkit-media-text-track-container {
+  transition: transform var(--media-caption-track-duration, 150ms) ease-out;
+  transition-delay: var(--media-caption-track-delay, 600ms);
+  transform: translateY(var(--media-caption-track-y, 0)) scale(0.98);
+  z-index: var(--media-caption-track-z, 1);
+  font-family: inherit;
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .media-skin > video::-webkit-media-text-track-container {
+    transition-duration: 50ms;
+  }
+}

packages/skins/src/shared/video-icon-state.css

@@ -0,0 +1,49 @@
+/* ==========================================================================
+   Icon State Visibility for Video Skins
+
+   Data-attribute-driven visibility rules for multi-state icon buttons.
+   Uses :is() with both element selectors (for HTML custom element wrappers)
+   and class selectors (for React rendered SVG elements).
+   ========================================================================== */
+
+/* --- All icons hidden by default --- */
+
+.media-button--play .media-icon--restart,
+.media-button--play .media-icon--play,
+.media-button--play .media-icon--pause,
+.media-button--mute .media-icon--volume-off,
+.media-button--mute .media-icon--volume-low,
+.media-button--mute .media-icon--volume-high,
+.media-button--fullscreen .media-icon--fullscreen-enter,
+.media-button--fullscreen .media-icon--fullscreen-exit,
+.media-button--captions .media-icon--captions-off,
+.media-button--captions .media-icon--captions-on {
+  display: none;
+  opacity: 0;
+}
+
+/* --- Active icon per state --- */
+
+/* Play: ended → restart */
+.media-button--play[data-ended] .media-icon--restart,
+/* Play: paused (not ended) → play */
+.media-button--play:not([data-ended])[data-paused] .media-icon--play,
+/* Play: playing (not paused, not ended) → pause */
+.media-button--play:not([data-paused]):not([data-ended]) .media-icon--pause,
+/* Mute: muted → volume off */
+.media-button--mute[data-muted] .media-icon--volume-off,
+/* Mute: volume low (not muted) → volume low */
+.media-button--mute:not([data-muted])[data-volume-level="low"] .media-icon--volume-low,
+/* Mute: volume high (not muted, not low) → volume high */
+.media-button--mute:not([data-muted]):not([data-volume-level="low"]) .media-icon--volume-high,
+/* Fullscreen: not fullscreen → enter */
+.media-button--fullscreen:not([data-fullscreen]) .media-icon--fullscreen-enter,
+/* Fullscreen: fullscreen → exit */
+.media-button--fullscreen[data-fullscreen] .media-icon--fullscreen-exit,
+/* Captions: not active → captions off */
+.media-button--captions:not([data-active]) .media-icon--captions-off,
+/* Captions: active → captions on */
+.media-button--captions[data-active] .media-icon--captions-on {
+  display: block;
+  opacity: 1;
+}