Move the console onto ReUI PRO

Install ReUI (MCP, skill, @reui registry, Tailwind v4, shadcn base-nova) and move
the shared UI onto it: Button, Tag, Check, Input/Textarea, Segmented, Alert, Panel,
Dialog, Tooltip, Menu and Select (Popover), Toast (sonner), the Table frame
(DataGrid), the Dashboard KPI strip, the shnt Ops palette, Geist and the type scale.

Design only: behaviour, texts and roles are unchanged. Tests that asserted the old
DOM were updated; the tests now format numbers in English wherever they run.
docs/reui-migration-plan.md records the plan and its decisions.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/ui/Button.tsx

@@ -0,0 +1,41 @@
+import type { ButtonHTMLAttributes, Ref } from 'react'
+import { Button as ReuiButton } from '@/components/ui/button'
+
+export type ButtonVariant = 'primary' | 'secondary' | 'danger'
+
+/*
+The console's button is ReUI's: the three variants map onto its `default`, `outline`
+and `destructive`, and the two sizes onto `default` and `sm`.
+
+`size="sm"` is the button for a table row. It existed as `.ib` copied across three
+modules and did not exist in DHCP, which used the large button: the same action
+("Edit") looked different depending on which screen you were on.
+*/
+const VARIANT = { primary: 'default', secondary: 'outline', danger: 'destructive' } as const
+
+export function Button({
+  variant = 'secondary',
+  size = 'md',
+  icon = false,
+  className,
+  ref,
+  ...rest
+}: ButtonHTMLAttributes<HTMLButtonElement> & {
+  variant?: ButtonVariant
+  size?: 'md' | 'sm'
+  /** No label: an icon only. The width comes from the icon, not from text. */
+  icon?: boolean
+  ref?: Ref<HTMLButtonElement>
+}) {
+  return (
+    <ReuiButton
+      ref={ref}
+      variant={VARIANT[variant]}
+      size={icon ? (size === 'sm' ? 'icon-sm' : 'icon') : size === 'sm' ? 'sm' : 'default'}
+      data-variant={variant}
+      data-icon={icon || undefined}
+      className={className}
+      {...rest}
+    />
+  )
+}