feat(ui): add semantic color contract and visual gate

[gcko]

PR checklist

• Ensure you have added or ran the appropriate tests for your PR.
• DCO signed

What type of PR is this?

Feature / accessibility

What this PR does / why we need it:

• Adds a role-first semantic color contract for comparison, structural change, and direction meanings while preserving the legacy DiffText.colorPalette API.
• Migrates shared grids, charts, lineage, CLL, row-count, legends, and edge renderers away from overloaded red/green presentation.
• Adds redundant symbols, labels, patterns, and accessible names so meaning survives grayscale, Protanopia, and Deuteranopia.
• Adds a production-renderer Storybook matrix with deterministic Light, Dark, and Grayscale visual baselines.
• Documents the semantic contract, contrast requirements, CVD review procedure, and canonical visual-capture environment.

Which issue(s) this PR fixes:

Part of DRC-2843.

This is the shared @datarecce/ui Phase B prerequisite. The recce-cloud-infra adoption remains a follow-up after this package is released, so this PR intentionally does not close the parent issue.

Special notes for your reviewer:

• Fresh verification on the pushed head: lint checked 677 files; all TypeScript projects passed; Vitest passed 194 files / 4,087 tests with 5 skipped; @datarecce/ui production and CSS builds passed; the semantic Playwright gate passed 5/5.
• Light, Dark, and Grayscale baselines were reviewed at 1440×1466. Chromium vision-deficiency emulation was reviewed for Protanopia and Deuteranopia in both themes.
• Two stale ExternalLink/Markdown Storybook interaction assertions and ten legacy Timeline visual selectors are byte-identical to main and are not introduced here.
• diff-cell-modified remains a rail-only compatibility selector for a value-summary mismatch producer; moving it to a dedicated semantic channel is safe follow-up debt.

Does this PR introduce a user-facing change?:

Yes. Comparison, structural-change, lineage, chart, and direction states now use consistent semantic colors with redundant non-color cues across light, dark, grayscale, and common color-vision deficiencies.