fix(painters/dom, super-editor): set explicit document text color floor (SD-3456)

[gpardhivvarma]

Closes #3456.

Summary

.superdoc-page (layout-engine page surface) and .sd-editor-scoped .ProseMirror (editor isolation surface) both relied on the browser default color. On dark-themed OSes that resolves to the canvastext system color (white), so any document text without an explicit <w:color> — auto-numbered list markers in particular — rendered invisible on the white page. There is no source CSS rule that sets color: rgb(255,255,255) in the repo; the reporter's devtools trace pointed at .superdoc-page because that was the highest-up element in the cascade where the color happened to resolve (via the user-agent default), not the rule that set it.

This PR sets an explicit color: var(--sd-layout-page-text, #000) floor on both surfaces. OOXML-explicit colors still win (inline style.color on runs has higher specificity than the inherited page color). Consumers customize via the --sd-layout-page-text token, documented in variables.css alongside --sd-layout-page-bg/--sd-layout-page-shadow.

Why two surfaces in one PR

.superdoc-page covers presentation-mode rendering (where the reported bug manifests). .sd-editor-scoped .ProseMirror covers the editor isolation surface for super-editor direct mounts (header/footer section editors, popovers, rich-text Field editors, etc.). Both are reverted to canvastext by isolation.css (all: revert) and both need the same floor. Bundling them avoids shipping the symptom-fix while leaving a sibling surface broken for the same reason.

Files

File	Change
packages/layout-engine/painters/dom/src/styles.ts	PageStyles.color?: string; DEFAULT_PAGE_STYLES.color = 'var(--sd-layout-page-text, #000)'; pageStyles() returns color: merged.color in the inline-style payload.
packages/layout-engine/painters/dom/src/styles.test.ts	3 new tests: default contract, consumer override path, DEFAULT_PAGE_STYLES exposure.
packages/super-editor/src/editors/v1/assets/styles/elements/prosemirror.css	Adds color: var(--sd-layout-page-text, #000) to .sd-editor-scoped .ProseMirror with an inline comment linking it to the page-painter fix.
packages/superdoc/src/assets/styles/elements/editor-scoped-color-floor.test.js	4 new tests guarding the editor-scoped rule (modeled on existing search-match-precedence.test.js).
packages/superdoc/src/assets/styles/helpers/variables.css	Adds --sd-layout-page-text: #000; to the "Styles: layout" section.

Test plan

• pnpm --filter @superdoc/painter-dom test -- styles.test.ts — 8/8 (3 new + 5 existing)
• pnpm --filter superdoc test — 1030/1030 (4 new + 1026 existing)
• Manual verification on macOS Chrome with system dark mode: open any DOCX with multi-level numbered lists (e.g. a legal MSA). Confirm clause numbers (1., 1.1, 1.1.1) are visible against the white page.
• Manual verification on light mode: confirm no visible change (text was black before via canvastext-on-light, still black after via the explicit floor).
• Layout-comparison run against published baseline — diff should show only the new color: ... property on the page element's inline style, no pixel deltas on Linux CI.

Reviewer notes / consumer impact

• Consumers using .superdoc-page { color: white } without !important to force dark text on the page will now lose to the inline style. The intended way to customize is --sd-layout-page-text (or pageStyles.color via the SuperDoc constructor). !important overrides still win.
• Token naming: --sd-layout-page-text is named after the layout page but is reused inside the editor isolation surface. Considered introducing a separate --sd-editor-text token but kept one shared token so theme authors set it once for both surfaces.
• Visual regression test not added: visual tests run on light-mode Linux CI where canvastext is already black, so a pixel-diff baseline would never catch this class. The CSS-content tests added here are the right safety net.

Follow-ups (not in this PR)

• Consider adding an architecture guard (sibling to Guards D/E in architecture-boundaries.test.ts) enforcing "every container hosting inherited document text must declare color explicitly in DEFAULT_*_STYLES."

[gpardhivvarma]

@caio-pizzol

[cubic-dev-ai]

No issues found across 5 files

_{Re-trigger cubic}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[gpardhivvarma]

hey @caio-pizzol just wanted to remind you