fix(Table): drop row tree ARIA outside treegrid

[AKnassa]

Part of #4681 (weekly a11y scan). Clears all 10 aria-conditional-attr baseline entries (TableTree x7, TableGroupedRows x3), plus the identical violation in the never-baselined TableTree::Row Click Expansion story.

What this does

The tree and groupedRows Table plugins set aria-expanded (and the tree plugin aria-level) on <tr> elements. Those attributes are only valid on rows inside a treegrid, and Astryx Table is a native <table>, so axe flags every story. Rows now carry no tree ARIA; the expand/collapse state stays announced by the chevron buttons, which already carry aria-expanded (the same pattern the rowExpansion plugin uses, which has zero baseline entries).

Why not role="treegrid" instead

Treegrid contracts the full ARIA grid keyboard model (roving tabindex, arrow-key cell navigation, focusable cells), none of which BaseTable implements. Screen readers would switch users into grid interaction mode and hand them an unnavigable widget. Building that model is a feature decision, not this fix. For groupedRows it is also semantically wrong: group headers are section separators of flat data, not tree parents.

Trade-off, stated plainly

Tree depth is now conveyed visually by indentation only. The removed aria-level was invalid in this context (and unreliably announced because of it), but assistive technology currently gets no programmatic depth cue. A follow-up candidate is announcing the level through the expander's accessible name; the changeset records the same trade-off so it lands as a decision, not a side effect.

What changed

• Rows lose aria-expanded (both plugins) and aria-level (tree plugin).
• The tree plugin's per-row ref/subscription machinery existed solely to apply row ARIA and is removed with it (net -77 lines); row-click expansion is unaffected and a dedicated regression review of the removal found no other dependents.
• Tests rewritten to assert rows never carry these attributes; the chevron buttons remain the single home of the expand state.
• doc.mjs updated to describe the actual semantics, including the visual-only depth limitation.
• Baseline: 10 entries removed, deletions only. Changeset (patch) includes a tr[aria-expanded] / tr[aria-level] test-migration hint.

Observation for a follow-up

Local audits report TableGroupedRows::Default::color-contrast and TableGroupedRows::Initially Collapsed::color-contrast as no longer occurring (stale baseline entries). Left untouched here; contrast entries are out of this PR's scope.

Verification

474/474 tests across all 22 Table test files, core typecheck, eslint clean, and the repo's axe audit with --fail-on-new: 0 violations across all 12 TableTree/TableGroupedRows stories.

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Modified Components

Table _{(@astryxdesign/core)} · View in Storybook

Metric	Before	After	Delta
Bundle Size (ESM)	N/A	N/A	N/A
Lines of Code	N/A	1938	-
Complexity	N/A	Very High (110)	-

Bundle Size Summary

Package	Size (ESM)	Size (CJS)	Gzipped
@astryxdesign/core	N/A	4.9KB	1.3KB

Accessibility Audit

Status: No accessibility violations detected.

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[cixzhang]

Hmm well this seems wrong. If we include tree data the table should probably be a treegrid.

[cixzhang]

I think the fix might be to apply the treegrid row when including tree data. We will likely need to make a version of useTreeGridFocus to achieve the right behaviors. It's quite a bit though. Let me know if you wanna do it!

[AKnassa]

Yes, happy to take it on.

Agreed treegrid is the right semantics. The row ARIA removed here was already treegrid shaped (1-based aria-level, aria-expanded on parents only), the container was the invalid part. Rough plan:

• role="treegrid" via transformTable, applied only when expandable rows exist so flat data keeps the plain table.
• Restore aria-level/aria-expanded on rows and add aria-posinset/aria-setsize, computed from the flattened visible list.
• New useTreeGridFocus: roving tabindex with row focus, Up/Down across visible rows, Right expands, Left collapses or jumps to parent, Home/End, Enter toggles where row-click expansion is on, focus preserved across expand/collapse re-renders. Role and keyboard ship together, a treegrid without arrow support would regress below the plain table.

Two questions before I start:

1. Do you have a reference useTreeGridFocus I should mirror? Related: is row focus enough for v1, or do you want cell navigation too? Either way the table becomes one tab stop, so in-cell widgets (sort headers, chevrons, selection checkboxes) stop being individually tabbable.
2. groupedRows is not tree data, and its change here just leaves the expanded state on the group toggle button. OK to split it into its own PR and keep this branch for the treegrid work?