## What kind of change does this PR introduce?
bug fix a11y `ExapndableVideo`
## What is the current behavior?
`ExpandableVideo` blurred thumbnail has `alt="Video guide preview"`
sitting behind an overlay that already reads "Watch video guide" making
screen readers announcing the same thing twice
## What is the new behavior?
- adds an optional `videoTitle` prop that names the video once and feeds
both the button's `aria-label` and the player's `title`.
## Test
1. visit `/docs/guides/functions`
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
- **Enhancements**
- Video previews in guides now display the relevant guide title.
- Partner introduction videos now include a descriptive title.
- Video controls and embedded players provide more specific
accessibility labels when titles are available.
- Preview images without meaningful alternative text are treated as
decorative to reduce redundant screen-reader output.
- **Bug Fixes**
- Guide titles with Markdown formatting now appear as clean, readable
text in video labels.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
