feat: Add skeleton loading support to table

[gethinwebster]

Add skeleton prop ({ totalRows: number }) that renders skeleton placeholder rows to fill the table while data is loading.

• skeleton.totalRows defines total visible rows (typically page size)
• Skeleton rows rendered = max(0, totalRows - items.length)
• Standard loading: items=[] + loading=true + skeleton -> all skeleton rows
• Progressive loading: items=[partial] + skeleton -> real rows + trailing skeleton
• A11y: visually-hidden row with ScreenreaderOnly loadingText before skeleton rows
• Skeleton rows use aria-hidden=true
• Includes interactive demo pages for both patterns

Description

Related links, issue #, if available: n/a

How has this been tested?

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.50%. Comparing base (ddbb532) to head (00a8498).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4583   +/-   ##
=======================================
  Coverage   97.50%   97.50%           
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  Files         947      948    +1     
  Lines       30248    30269   +21     
  Branches    11021    11029    +8     
=======================================
+ Hits        29493    29514   +21     
- Misses        708      748   +40     
+ Partials       47        7   -40     

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