feat(components): DataTable (RAC + TanStack v8) [spike]

[ccschmitz-launchdarkly]

Spike — for design review via Chromatic, not to merge as-is.

A higher-level DataTable composed on the LaunchPad RAC Table + TanStack Table v8. RAC owns markup/keyboard/a11y/selection/sort-UI/DnD/resize; TanStack is the headless model for filtering, sorting, column visibility, and column order.

Included

• DataTable<TData> — declarative columns (TanStack ColumnDef) + data, with: freeform search, sorting (incl. defaultSorting), row selection, column show/hide, resize, density (default/compact/tight), click-row-to-open (onRowAction / single-select replace), and column drag-reorder (grip handle → TanStack columnOrder, dep-free HTML5 drag; pin with meta.enableReorder: false).
• Cell content helpers (DataTableCells): TwoLineCell, NumericValue, DeltaValue, StatusCell, TagCell, MonoValue — matching the Figma "Table BETA" content set.
• Header/border styling matched to the o11y traces design (node 2829-54659).
• Stories: Overview, Traces List, With Selection, Density, Numeric Columns, Empty.

Review in Chromatic

The Chromatic check on this PR publishes a Storybook for the design team → Components / Collections / DataTable.

Notes / follow-ups (see spikes/launchpad-datatable/SPEC.md)

• Keyboard column-reorder (mouse-only today).
• Header sort icon is RAC's caret vs the design's down-arrow, and no per-column menu — both live in the shared RAC Table (design/LP decision).
• No changeset yet (spike).
• The real observability AlertsTable migration proving this out lives in a separate gonfalon PR.

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[ccschmitz-launchdarkly]

Superseded — consolidating into a single gonfalon PR: the DataTable now incubates in @gonfalon/launchpad-experimental alongside its real proof-out (AlertsTableV2), so the component + consumer live in one PR. See launchdarkly/gonfalon#66872. Will graduate to @launchpad-ui/components once the API settles.