feat: VirtualTable (headless / F3-A2) P5 default styling matches Cloudscape Table

[gethinwebster]

VirtualTable (headless / F3-A2) — P5 default styling rework

Design-study prototype thread F3-A2 (headless useVirtualGrid core + compound Cloudscape skin). This P5 rework brings the prototype to default visual parity with the existing Cloudscape Table, on the Brazil-mirrored dev-v3-gethinw-virtualtable-headless branch.

What changed (P5 rework)

• Default styling now matches Cloudscape Table by reusing Table design tokens / existing Table styles: borders, header treatment, row height/density, hover + selected state hooks, sticky-header look, wrapping (single-line truncate by default = wrapLines=false, opt-in .cell-wrap). No look reinvented.
• Native scrollbar only — no ::-webkit-scrollbar, no overlay/synthetic scrollbar; the virtualization viewport scrolls natively.
• Change is confined to the compound skin's styles.scss; the headless useVirtualGrid core carries no CSS.

Local gates (green)

npm run build exit 0 · full npm run lint 0 errors · jest virtual-table suites green.

Supersedes

Supersedes the P4 draft PR #4742 (a GitHub PR head branch cannot be repointed onto a new branch).

Human-gated (out of scope for this automated rework)

• Official Cloudscape API review + design/release sign-off.
• F3-A2 ships a compound object-literal default export; the shared documenter / single-default-export cross-cutting meta-tests do not model that shape (same pre-existing P4 integration gap flagged on the F1-A2 compound thread PR feat: VirtualTable (composable / F1-A2) P5 default styling matches Cloudscape Table #4748). Any CI failures in those cross-cutting harness/documenter checks are pre-existing at the P4 base (31646ec), not a styling regression, and are left for human governance — the RESOLVED F3-A2 API was deliberately not distorted to satisfy the harness.