Web Shell Table Selection Statistics

Summary

Add a read-only statistics strip to advanced Web Shell markdown tables. When a user selects cells, the existing toolbar will show selected, non-empty, and numeric counts. If the selection contains numeric values, it will also show sum, average, minimum, and maximum.

The standalone daemon Web Shell enables advanced markdown tables so the new statistics and the existing table interactions are available in that surface.

Goals

Make quick numerical inspection possible without copying data into Excel.
Keep statistics aligned with the existing visible-cell selection and TSV copy behavior.
Reuse the table's existing number parser so sorting, filtering, and statistics agree.
Preserve recognizable percent and currency formatting when the selected numeric cells use one consistent format.

Non-goals

Formula evaluation, unit conversion, date statistics, or editable cells.
Discontiguous selections or statistics over filtered-out and hidden cells.
User-configurable metrics, popovers, or new dependencies.

Behavior

Statistics are computed from the selected rectangle in visibleRows and the currently visible column order. Blank cells count as selected but not non-empty. Text cells count as non-empty but not numeric. Arithmetic metrics use numeric cells only, and are hidden when no numeric cells are selected.

The toolbar renders compact inline metrics. It retains the existing TSV copy action and wraps naturally on narrow screens.

Uniform percent selections display arithmetic results as percentages. Uniform currency selections retain their common currency symbol. Mixed numeric formats fall back to locale-formatted plain numbers.

Implementation

Add a pure selection-statistics helper alongside the existing selection and clipboard helpers. The component derives its result with useMemo; no new mutable state is required. Add small formatting helpers for locale-aware numbers, percentages, and common currency symbols.

The enhanced table limit is 500 rows by 50 columns, so a full-selection scan is bounded at 25,000 cells. The existing animation-frame throttling for drag selection keeps recomputation within the current interaction cadence.

Verification

Unit tests cover numeric, mixed text/blank, currency, percent, reordered, hidden-column, filtered, updated-data, and localized selections. A daemon Web Shell browser check verifies drag selection, live metric updates, and wrapping in the rendered UI.