[lab] Visual polish for RichTextEditor and toolbar - #4818

Summary

Refreshes the lab RichTextEditor so it looks and behaves like an Astryx form field, adds a compact formatting toolbar, and replaces the browser URL prompt with an Astryx link dialog.

This revision is intentionally scoped to @astryxdesign/lab: it does not modify Toolbar, ToggleButton, MoreMenu, OverflowList, useListFocus, or any other Core component.

The component remains named RichTextEditor: it is an extensible Lexical authoring surface with formatting, plugins, nodes, history, and serialization—not only a rich-text value input.

Field visuals and sizing

• Matches TextArea/TextInput for the resting outline, hover treatment, focus-within ring, radius, disabled/read-only treatment, and semantic status colors.
• Aligns placeholder and entered text by sharing the same body typography, line height, responsive coarse-pointer sizing, and content inset.
• Adds minHeight: SizeValue for the editable surface. Numbers are pixels, strings are CSS lengths, the default remains 4.5rem, and content can grow beyond the minimum.
• Adds a dedicated toolbar slot before the padded editing surface, keeping controls flush with the top edge and in the correct visual and keyboard order.
• Corrects accessible-name wiring: the contenteditable has its own input ID and references a real label ID.

Status treatment

• Adds the same in-field semantic status icon used by Astryx inputs.
• Supports statusVariant="attached" | "detached" | "tooltip":
  • attached — the icon stays in the editor and the message connects below the field.
  • detached — the message sits below as its own status row with an icon.
  • tooltip — a focusable in-editor icon reveals the message without reserving a message row.
• Error sets aria-invalid; descriptions, status messages/tooltips, character count, and keyboard hints remain correctly composed through aria-describedby.

Formatting toolbar

• Uses the existing Astryx Toolbar with small controls; ToggleButton size is passed explicitly inside Labs, so no Core sizing behavior changes.
• Groups Undo/Redo, block formatting, and inline formatting with vertical dividers.
• Combines Paragraph, Heading 1–3, bulleted list, numbered list, and block quote into one block-format Selector.
• Leaves the Selector's standard adaptive popover placement unchanged.
• Uses ToggleButtons for Bold, Italic, Underline, Strikethrough, Inline code, and Link, with active state synchronized to the Lexical selection.
• Removes the experimental AI action.

Narrow-width behavior

• Keeps every action as a direct toolbar control; there is no More menu or OverflowList dependency.
• Wraps the complete action row in a Labs-only, non-wrapping horizontal scroll container.
• Preserves Toolbar's existing roving-arrow keyboard behavior; focusing an off-screen control scrolls it into view.
• Adds resizable and 240–900 px stress-test stories.
• Browser verification asserts overflow-x: auto and scrollWidth > clientWidth at 340 px.

Link workflow

• Replaces window.prompt with an Astryx Dialog containing a URL TextInput and standard Cancel/Add/Update/Remove actions.
• Uses the canonical Dialog header/content/footer layout, removing the doubled header inset and aligning all sections to one padding rhythm.
• Supports the toolbar action and Cmd/Ctrl+K while preserving the Lexical selection.
• Sanitizes URLs to http, https, mailto, or tel; unsafe schemes are rejected.
• Keeps the existing promptForUrl extension point for consumers with a synchronous custom URL flow.
• Preserves new-tab link attributes in Lexical node data so they serialize and round-trip.

Screenshots

These are GitHub-hosted PR attachments and are not committed to the repository.

Field focus, placeholder alignment, and minHeight

Status variants

Attached error	Detached warning

Compact toolbar and block-format selector

Horizontal toolbar scroll

Astryx link dialog

Validation

• 86 focused RichTextEditor tests
• ESLint on changed Labs and Storybook files
• Lab documentation typecheck and package build
• Storybook typecheck and production build
• Browser assertion and screenshot pass for narrow-width scrolling and the link dialog
• Repository sync, package-boundary, changeset, demo-media, executable-bit, and CLI-structure checks
• PR accessibility and RTL audits