[codex] Fix Safari grid horizontal scrolling

[gregory-boch-prisma]

Summary

Fixes horizontal scrolling in Prisma Studio wide grids on Safari by keeping the shared table wrapper as a plain overflow scroller instead of making the scroll container itself a flex formatting context.

Root Cause

The grid table already pins its width to the computed column sizes. The wrapper around that table also had display: flex, which Chromium tolerated, but Safari can fail to expose the expected horizontal scroll range for wide table content inside an overflow flex container.

Changes

• Remove flex items-start from the shared table wrapper.
• Add min-w-0 so the overflow container can shrink inside Studio's flex layout while preserving horizontal overflow.
• Add a DataGrid layout regression test asserting the wrapper remains a plain overflow-auto scroller.
• Add a localStorage mock in that test file so it runs reliably in this Node/happy-dom setup.

Validation

• pnpm test:ui ui/studio/grid/DataGrid.layout.test.tsx
• Manual browser check with pnpm demo:ppg at http://localhost:4310 using the seeded public.all_data_types table.
• Captured screenshots at the left edge and after horizontal scroll; the later screenshot shows the grid successfully scrolled to later columns (double_col, inet_col).

Note: pnpm test:ui ui/studio/grid/DataGrid.virtualization.test.tsx currently fails before assertions in this checkout because globalThis.localStorage lacks getItem in that test environment. The focused layout test includes a local mock and passes.

[ghost]

Compute preview deployed.

Branch: codex/fix-safari-grid-horizontal-scroll
Service: codex-fix-safari-grid-horizontal-scroll
Preview: https://cmou2cw020fmryhdx8pgyytdt.cdg.prisma.build
Version: https://cv-ceaf5651dfde.cdg.prisma.build