fix: reserve space for sort indicator to prevent header layout shift (#995)

[alpurkan17]

Summary

Clicking a sortable column header causes the header row to reflow because the TableSortLabel icon appears/disappears dynamically, pushing cell content and triggering width recalculation.

Add white-space: nowrap on the header cell to prevent text reflow, and reserve width: 18px for the sort icon (opacity 0 when inactive) so the space is always accounted for in the layout.

Validation

• npm run lint — clean
• npm run test — 27 passed

Closes #995

[alpurkan17]

@anderdc @LandynDev ready for review

[anderdc]

Please scope this down to what #995 asks for. Keep: the DataTable.tsx sort-indicator fix — whiteSpace nowrap on the header cell and the TableSortLabel icon opacity/width sx. Drop: the linkBehavior.tsx LinkTableRow rewrite and the getRowHref JSDoc change in DataTable.tsx. Those are unrelated to #995 — and they're the same LinkTableRow change as PR #1130 / issue #1127, which were closed as not planned.

[alpurkan17]

@anderdc changes addressed per your review. Commit e634a1c scoped the PR down to only the DataTable.tsx sort-indicator fix (7 lines). LinkTableRow changes have been dropped. Please re-review.

[alpurkan17]

Scoped down per review — DataTable.tsx sort-indicator fix only, linkBehavior.tsx removed.