feat: add Rich Text Editor component (v0) [WIP]

[ernst-dev]

Description

[WIP / DRAFT] First-cut (v0) of a Rich Text Editor component for Cloudscape, opened for early feedback. Additive and fully opt-in — no existing components are changed.

This implements a minimal WYSIWYG editor: a formatting toolbar (bold / italic / underline / strikethrough / bulleted list / numbered list / link) over a contenteditable region, with a controlled value / onChange (HTML string) API built on Cloudscape primitives and design tokens.

Related links, issue #, if available: AWSUI-60329 (Cloudscape contribution request: Rich Text Editor)

v0 scope (done in this PR)

• New public component RichTextEditor (src/rich-text-editor/) with React.forwardRef + imperative focus().
• Controlled value (HTML string) / onChange, plus onFocus / onBlur.
• Toolbar controls: bold, italic, underline, strikethrough, bulleted-list, numbered-list, link; configurable/orderable via toolbarControls.
• Props: placeholder, disabled, readOnly (toolbar hidden), ariaLabel, i18nStrings, form-field context integration (invalid / warning / controlId), and BaseComponentProps.
• Styling via internal styles + design tokens (styles.scss); role="toolbar" / role="textbox" with aria-multiline.
• Fully JSDoc-documented interfaces (interfaces.ts).
• Test-utils DOM wrapper (findRichTextEditor, findToolbar, findToolbarButton, findContent, getValue).
• Dev pages: simple.page.tsx and permutations.page.tsx.
• 14 unit tests. Documenter + test-utils snapshots regenerated for the new public component.

Remaining work (follow-ups — intentionally out of scope for v0)

• Replace document.execCommand (deprecated) with a Selection-API / lightweight editor core.
• Built-in HTML sanitization (v0 delegates sanitization to the consuming app; see interfaces.ts).
• Accessible link dialog instead of the native window.prompt placeholder; validate URLs via checkSafeUrl.
• Toolbar button active/pressed state reflecting the current selection (aria-pressed, queryCommandState).
• Additional formatting from the ticket: text type (H1–H5, paragraph, code, block quote, sub/superscript), text color / background color, and text alignment (left/center/right/justify).
• Full a11y pass (keyboard toolbar roving tabindex, screen-reader verification), i18n message registration, integration/a11y/motion tests, and public documentation (Usage tab).
• Analytics metadata, style API parity with other form controls, RTL review.

How has this been tested?

• eslint (component, pages, test-utils, build-tools) — pass.
• stylelint on component SCSS — pass.
• gulp quick-build and full gulp build (production, incl. dev pages + documenter) — pass.
• Unit tests: src/rich-text-editor — 14/14 pass.
• All-component functional tests (base props, naming, test-utils, SSR, form-field, etc.) — 1843/1843 pass.
• Snapshot suites (documenter / test-utils wrappers / selectors) regenerated and re-verified clean.

Reviewers can explore the component via the rich-text-editor dev pages (simple, permutations).

Note: This is a WIP draft to align on the API shape and scope before investing in the full feature set and documentation. Feedback on the public API and v0 boundaries is very welcome.

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[codecov]

Codecov Report

❌ Patch coverage is 94.31818% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.60%. Comparing base (f97729a) to head (e0cc8fc).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/rich-text-editor/index.tsx	93.24%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4823      +/-   ##
==========================================
- Coverage   97.61%   97.60%   -0.01%     
==========================================
  Files         952      954       +2     
  Lines       30816    30904      +88     
  Branches    11318    11343      +25     
==========================================
+ Hits        30081    30164      +83     
- Misses        688      693       +5     
  Partials       47       47              

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