## Why

The 2026-04-25 test-suite audit (`/mnt/s/web/genesis/docs/superpowers/specs/2026-04-25-test-suite-audit.md` §2 row 2) flagged "no visual regression" as a critical gap. Stories existing in Storybook is not visual coverage — pixel drift between commits goes unnoticed until a user reports it. CLAUDE.md's "Web App & Page Verification" section requires verifying the rendered DOM contains expected content; visual regression is the strongest automated form of that check.

This change introduces baseline-screenshot coverage on two surfaces:

1. **Playwright e2e** — `expect(page).toHaveScreenshot()` baselines for every page in `apps/<app>/e2e/`.
2. **Storybook** — every `*.stories.tsx` story produces a screenshot baseline per variant via `@storybook/test-runner`.

Both paths share the same threshold, viewport pinning, and animation-disabling discipline so a single `--update-snapshots` workflow covers them.

## What Changes

### New surface in `@suaveplan/testing-e2e`

- `configureVisualRegression(config?)` — emits a `PlaywrightTestConfig` fragment with `expect.toHaveScreenshot.maxDiffPixelRatio: 0.005`, `expect.toHaveScreenshot.animations: 'disabled'`, viewport pinned to 1280×720, `prefers-reduced-motion: reduce` forced.
- `prepareForVisual(page)` — disables animations, waits for `networkidle` + `document.fonts.ready`, sets `prefers-reduced-motion`. Called inside e2e specs before `toHaveScreenshot`.
- Baselines stored under `apps/<app>/e2e/__snapshots__/<platform>/<spec>/<test>.png`.
- Structured error codes under `TESTING_E2E.VISUAL.*` (`PIXEL_DIFF_EXCEEDED`, `BASELINE_MISSING`, `FONTS_NOT_READY`, `VIEWPORT_MISMATCH`).

### New surface in `@suaveplan/testing-dom`

- `createStorybookTestRunnerConfig(opts)` — returns the `@storybook/test-runner` config with the visual hooks pre-wired (`postVisit` snapshot capture, threshold matching the e2e path).
- `pinStoryEnvironment(page)` — locks viewport, font loading, and reduced-motion for stories.
- Structured error codes under `TESTING_DOM.STORYBOOK_VISUAL.*` (`PIXEL_DIFF_EXCEEDED`, `BASELINE_MISSING`, `RUNNER_LOAD_FAILED`).

### Modified surface

- Storybook stories MUST register through the test-runner config so every variant produces a baseline.
- Theme/locale decorators MUST honour the `pinStoryEnvironment` contract (deterministic theme + locale per story file).
- `--update-snapshots` runs MUST land in a separate review-tagged commit per genesis policy.
- Cross-link to the `enterprise-testbed-verification` change: visual diffs feed the release-readiness gate.

## Capabilities

### New Capabilities

(none — extensions to existing `testing-e2e` and `testing-dom` capabilities)

### Modified Capabilities

- `testing-e2e`: adds `configureVisualRegression`, `prepareForVisual`, `TESTING_E2E.VISUAL.*` error codes, baseline-storage layout requirement, per-OS matrix requirement.
- `testing-dom`: adds Storybook test-runner config factory, `pinStoryEnvironment`, `TESTING_DOM.STORYBOOK_VISUAL.*` error codes, per-story baseline requirement.

## Impact

- **Affected code:** `/mnt/s/web/genesis/packages/testing/testing-e2e/src/visual/**`, `/mnt/s/web/genesis/packages/testing/testing-dom/src/storybook-visual/**`, every consumer with stories or e2e specs.
- **Catalog adds:** `@storybook/test-runner` to `catalogs.testing` in root `package.json`. (Pixel diffing reuses Playwright's built-in `pixelmatch`-equivalent — no extra catalog dep.)
- **Coverage:** 100% Istanbul on every helper module per project rule.
- **Baselines:** committed to repo under `__snapshots__/`. Per-OS subdirectory matches CI matrix (linux / darwin / win32). CI updated to run the full matrix or skip the platform check explicitly.
- **No version bump:** both packages stay at `0.1.0`.