docs: add SearchInput tabular-nums documentation (GrantFox FWC26)

docs/tabular-nums-search-input.md

@@ -0,0 +1,137 @@
+# Tabular Numerals in SearchInput (GrantFox FWC26)
+
+## Summary
+
+`font-variant-numeric: tabular-nums` is applied to every amount and count
+displayed in the `SearchInput` component. This ensures digits occupy a fixed,
+equal-width cell so numeric values (result counts, status chip counts, monetary
+amounts) do not shift surrounding layout when values update — for example, "1"
+and "999" take the same horizontal space as a column.
+
+This is part of the GrantFox FWC26 campaign (Stellar Wave) UI/UX requirement
+to align digits vertically across both light and dark themes.
+
+---
+
+## Files changed
+
+| File | Change |
+|------|--------|
+| `src/pages/SearchInput.tsx` | Applied `font-variant-numeric: tabular-nums` via inline styles and `numeric-tabular tabular-nums` CSS classes to the container, input field, result count badge, amount badge, and all status chip count spans. |
+| `src/styles/typography.css` | Contains the `.numeric-tabular` / `.tabular-nums` utility classes that provide the CSS property at the class level (imported globally via `main.tsx`). |
+| `src/pages/SearchInput.test.tsx` | Added focused test suite `"Tabular-nums numeric displays (#740 / b#063)"` covering all numeric display elements. |
+
+---
+
+## Where tabular-nums applies in SearchInput
+
+| Element | Mechanism |
+|---------|-----------|
+| `.search-input-container` wrapper | `className="numeric-tabular tabular-nums"` + `style={{ fontVariantNumeric: 'tabular-nums' }}` |
+| `<input>` text field | `className="search-input-field tabular-nums numeric-tabular"` + inline style |
+| `search-amount-display` span | `className="search-input-amount tabular-nums numeric-tabular"` + inline style |
+| `search-result-count` span | `className="search-input-result-count tabular-nums numeric-tabular"` + inline style |
+| Each status filter chip `<button>` | `className="search-status-chip numeric-tabular tabular-nums …"` + inline style |
+| Per-chip count span `(.search-status-chip-count)` | `className="search-status-chip-count numeric-tabular tabular-nums"` + inline style |
+
+The container-level `fontVariantNumeric: 'tabular-nums'` provides a CSS cascade
+fallback so any future numeric child added without an explicit class still
+renders with tabular numerals.
+
+---
+
+## Implementation approach
+
+Two complementary layers ensure consistent coverage:
+
+1. **Inline `style={{ fontVariantNumeric: 'tabular-nums' }}`** — applied
+   directly to each element that renders a number. This is the highest-specificity
+   guarantee and works even if the CSS file is not loaded.
+
+2. **CSS utility classes `numeric-tabular` / `tabular-nums`** — defined in
+   `src/styles/typography.css` and imported globally. The canonical class is
+   `.numeric-tabular`; `.tabular-nums` is kept as an alias for backwards
+   compatibility with existing code.
+
+This two-layer approach matches the pattern established in `ApiCard`,
+`ApiDetailPage`, `ApiUsage`, and `MarketplacePage`.
+
+---
+
+## CSS utility
+
+Defined in `src/styles/typography.css`, imported globally via `src/main.tsx`:
+
+```css
+.numeric-tabular,
+.tabular-nums {
+  font-variant-numeric: tabular-nums;
+}
+```
+
+Use `.numeric-tabular` for new code (canonical name). `.tabular-nums` is a
+backwards-compatible alias only.
+
+---
+
+## Props that render numeric values
+
+| Prop | Rendered as | Example output |
+|------|-------------|----------------|
+| `resultCount?: number` | `"N result(s)"` badge | `24 results` |
+| `totalCount?: number` | Drives `"all"` chip count | `(48)` |
+| `amount?: number` | Dollar-formatted amount badge | `$1,250` |
+| `statusCounts?: Partial<Record<SearchStatusFilter, number>>` | Per-chip count `(N)` | `(36)` next to "Operational" |
+
+---
+
+## Tests
+
+Test suite `"Tabular-nums numeric displays (#740 / b#063)"` in
+`src/pages/SearchInput.test.tsx` verifies:
+
+| Test | What it checks |
+|------|----------------|
+| `applies tabular-nums and numeric-tabular CSS classes to container and status chips` | `.search-input-container` has both classes; each status chip button has both classes and the inline style. |
+| `renders numeric status counts with tabular-nums formatting when statusCounts is provided` | `statusCounts` prop causes `(N)` spans to render with `tabular-nums` class and inline style. |
+| `renders resultCount readout with tabular-nums styling` | `resultCount` badge has correct text, classes, and inline style. |
+| `renders amount display with tabular-nums styling` | `amount` badge has correct text (`$1,250`), classes, and inline style. |
+
+Run with:
+
+```bash
+npx vitest run src/pages/SearchInput.test.tsx
+```
+
+All 14 tests (including 4 tabular-nums focused tests) pass.
+
+---
+
+## Accessibility notes
+
+`font-variant-numeric: tabular-nums` is a font rendering hint only. It does
+not affect content, semantics, or ARIA attributes, so there is no WCAG impact.
+The visual benefit is that columns of numbers stay horizontally stable as
+values change, reducing cognitive load for users scanning live-updating counts.
+
+The status chips remain fully accessible:
+- `role="button"` with `aria-pressed` for toggle state
+- `aria-label` includes the count when `statusCounts` is provided
+- `aria-description` explains the colour-blind-safe pattern texture used on each chip
+
+---
+
+## Browser support
+
+`font-variant-numeric: tabular-nums` is supported in all modern browsers
+(Chrome 21+, Firefox 34+, Safari 9.1+, Edge 79+). On browsers that do not
+support it the property is silently ignored and proportional numerals are used
+— no regression in layout or semantics.
+
+---
+
+## Related
+
+- `docs/tabular-nums-marketplace.md` — same FWC26 change applied to `MarketplacePage`
+- `src/styles/typography.css` — shared CSS utility definitions
+- `src/pages/SearchInput.tsx` — component source