perf(html): re-render sliders on resize only for edge thumb alignment

[taekop]

Closes #9400

Summary

media-slider, media-time-slider and media-volume-slider called requestUpdate() on every resize. Only thumb-alignment="edge" reads the slider's size, so with the default center alignment each resize re-applied the same attributes and CSS variables.

Changes

• The resize callback now requests an update only when thumbAlignment is edge.
• Edge-aligned sliders still re-render on resize, so the behavior from fix(html): thumb edge alignment jump v10#766 is unchanged.
• Changing thumb-alignment still re-renders through the normal property update.

Testing

• New test in each slider element suite: a resize does not call requestUpdate() for center and calls it once for edge. The three tests fail without the change.
• vp test run in packages/html (450 passed), packages/react (584 passed) and packages/core (1474 passed). The 4 menu/tests/module-graph.test.ts failures in html and react also happen on main in my checkout. They come from a space in my local path (%20 in the resolved file path).
• pnpm typecheck, vp check --no-lint and vp lint on the changed files.

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