[NO-ISSUE] test(storybook): cover light theme, tablet and mobile in the visual matrix

[robsongajunior]

Summary

16 files modified another are added images

The visual regression layer screenshotted every story exactly once — dark theme at 1280×720 — so light mode, tablet, and mobile were never tested, even though light tokens have full parity and the responsive spacing/typography tokens reshape nearly every story below md.

Every story is now snapshotted in a 6-mode matrix: dark|light × desktop(1280×720)|tablet(768×1024)|mobile(375×667), aligned to the theme's token breakpoints. The Storybook toolbar gets the same DS viewports.

• .storybook/visual-modes.js (new): single source of truth — viewports, theme classes, mode matrix, snapshot naming, resolveModes (per-story narrowing + VISUAL_MODES env filter). Feeds both the test-runner and preview.js (toolbar viewports + theme decorator classes).
• test-runner.js: per-story mode loop (resize → theme class flip → double-rAF settle → fonts/images settled → screenshot). Failures are collected per mode so one run writes every failing diff. The freeze style now also mirrors preview.css's canvas-transition selectors (they outrank * in specificity — a theme flip would otherwise animate 0.4s mid-screenshot). New: explicit image-settle await (load/error + decode()) — networkidle alone let the remote avatar photo flake both ways.
• Baseline naming (compat): dark-desktop keeps the bare story id, so the 317 committed baselines stay byte-identical; other modes get --<mode> suffixes. Verified locally: full matrix = 1,890 snapshots, stable across back-to-back runs (0 diffs, ~2 min).
• Per-story control: parameters.visual: false unchanged; new visual: { modes: [...] } narrows the matrix (used only by the 3 foundation token galleries, whose mobile reflow approaches Chromium's 16384px capture ceiling — both themes still covered at desktop).
• CI: the governance visual job is sharded ×4 (mirrors the Vitest job) via VISUAL_SHARD; per-shard diff artifacts. Baseline-regen workflow: timeout 60m + optional modes input for partial regeneration. testTimeout: 30000 in the jest layer (default 5s was sized for one screenshot).
• Stories: Breadcrumb's ResponsiveCollapsed now uses the DS mobile viewport (the old mobile1 preset no longer exists) — its mobile snapshot finally captures the collapsed ellipsis state.
• Docs: docs/OVERVIEW_TESTS.md Layer-2 sections updated (matrix, naming, determinism table, sharding, correct workflow filename).

Notes

• The visual job is expected red on this PR until the Linux baselines land: next step is dispatching app-storybook-generate-baseline.yml on this branch (update_baselines=true), then committing the ~1,573 new PNGs here (existing 317 must show zero modifications — that's the compat invariant).
• No release: nothing under packages/** changes (test type, no bump).
• No new dependencies.
• Root storybook:test:visual:update:baseline script now dispatches against the current branch instead of the deleted test/webkit.