feat(ui): component redesign pass and fixes, release ui 0.8.87

Redesign
- Shared field foundation rules (duplicated across 15 form components and
  emitted globally) are now identical everywhere, so later copies no longer
  silently override earlier redesigns.
- Drawn checkbox and radio controls, white switch thumbs (the thumb was the
  text colour, a black blob in light mode), recessed field wells, keycap
  actions in Modal, Drawer, Popover, Toaster, Pagination, Stepper, DataTable.
- Menus (Dropdown, ContextMenu, Popover, Select dropdown, Navbar panels) share
  one flat raised panel with neutral hover rows and mono section labels.
- Alerts with an accent rail and icon chip; card headers without the grey
  band; accordion, collapse, list, list group, timeline, stats, metrics,
  chat, skeleton, avatar group, clipboard, splitter, section, sidebar,
  navbar and upload progress restyled.
- Chart rebuilt: nice y-axis ticks, gridlines, rounded bars, line and area
  modes, hover tooltips, hidden series leave the scale.

Fixes
- Checkbox and radio labels toggle their input again (empty for="" broke it).
- TimePicker kept every clicked time pressed; only the chosen hour and
  minute are pressed now, and nothing is pressed before a value exists.
- ColorPicker hex readout now follows the picked colour.
- Disabled FileInput no longer shows the native file-input text.
- Date and time panels float instead of pushing content.
- ContextMenu opened at the pointer closes on scroll.
- Drawer left/top/bottom placements slide from their own edge again.
- Image-only Card no longer renders an empty body strip.
- Timeline supports item.time, current/upcoming states, sizes and
  compact/alternate variants; showcase demos use distinct variants.
- ChatBubble: delivery receipts (sending/sent/delivered/read/failed/error)
  and meta aligned to its bubble.

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

packages/ui/components/MetricGrid.wrn

@@ -107,8 +107,8 @@ component MetricGrid {
       padding: 1.25rem;
       color: var(--wrn-color-text-muted);
       background: var(--wrn-color-surface-soft);
-      border: 1px dashed var(--wrn-color-border);
-      border-radius: 0.9rem;
+      border: 1px dashed var(--wrn-color-border-strong, var(--wrn-color-border));
+      border-radius: var(--wrn-radius);
       text-align: center;
     }
     .wrn-metric-grid__frame {
@@ -187,11 +187,6 @@ component MetricGrid {
 
     .wrn-metric-grid[data-variant="soft"] .wrn-metric-grid__surface {
       background:
-        linear-gradient(
-          135deg,
-          color-mix(in srgb, var(--wrn-color-primary) 8%, transparent),
-          transparent 62%
-        ),
         var(--wrn-color-surface-raised);
     }