Stack a bar's readings, and stop widgets taking the phone sideways

A bar drew its nested reading on top of the outer one in --chart-5, which
measures 2.53:1 against --primary and lost the 3:1 guideline for non-text. The
readings now partition the fill end to end, up to three of them, in a token of
their own: --primary-nested, the primary hue a few steps deeper, 3.14:1 light
and 3.12:1 dark. It cannot also clear 3:1 against --muted — in dark those two
are 5.82:1 apart and a colour 3:1 from both would need a 9:1 gap — so a segment
is drawn inside a gutter of outer fill rather than ever bordering the track,
which is what separates neighbours too, and what caps the count at three. A
nested value larger than its outer used to spill onto the track; it is clamped.
`inner` still reads as a single binding, so no dashboard needs migrating.

On a phone, .widget-grid took its width from the widest thing any widget held —
a truncating flex item still offers its whole unwrapped line as a min-content
contribution — and a handful of widgets had no floor of their own: the uPlot
legend is a table, a fieldset carries min-inline-size: min-content from the UA
sheet, and buttons are whitespace-nowrap. Each is capped now. A widget's body
scrolls rather than clipping, so long text stops painting over the title.

Gauges and bars move between readings instead of jumping, and a segmented
control slides one thumb rather than recolouring cells. The gauge arc is drawn
whole and revealed by its dash, because `d` cannot be transitioned.

UplotChart pushed new readings only when the point count changed, so once a
rolling window was full a refetch left the old values on screen.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uq8mtNb97A7praJLyeEYgs

frontend/src/components/Common/RangePicker.tsx

@@ -1,3 +1,7 @@
+// The segmented shape's thumb transition lives beside the dashboard's own
+// widgets, and CSS is chunked per entry — so the rule is pulled in wherever
+// this picker is used, or the two copies of one shape would move differently.
+import "@/components/Dashboard/dashboard.css"
 import { cn } from "@/lib/utils"
 
 /**
@@ -48,22 +52,41 @@ export function RangePicker({
   value: Range
   onChange: (range: Range) => void
 }) {
+  const chosen = RANGES.findIndex((range) => range.hours === value.hours)
   return (
+    // A `fieldset` carries `min-inline-size: min-content` from the UA sheet,
+    // which no width utility overrides. Equal tracks and no gap put the
+    // sliding thumb at its share of the padded box without measuring — a grid
+    // rather than a flex row because `flex-1` under `w-fit` sizes the segments
+    // to a share of the widest label instead of to the label itself.
     <fieldset
       data-testid="range-picker"
-      className="flex w-fit items-center gap-1 rounded-full border border-border p-1"
+      className="relative grid w-fit min-w-0 items-center rounded-full border border-border p-1"
+      style={{
+        gridTemplateColumns: `repeat(${RANGES.length}, minmax(0, 1fr))`,
+      }}
     >
       <legend className="sr-only">Time range</legend>
-      {RANGES.map((range) => (
+      {chosen >= 0 ? (
+        <span
+          aria-hidden
+          className="widget-segment-thumb pointer-events-none absolute inset-y-1 rounded-full bg-accent"
+          style={{
+            left: `calc(0.25rem + ${chosen} * (100% - 0.5rem) / ${RANGES.length})`,
+            width: `calc((100% - 0.5rem) / ${RANGES.length})`,
+          }}
+        />
+      ) : null}
+      {RANGES.map((range, index) => (
         <button
           key={range.label}
           type="button"
-          aria-pressed={range.hours === value.hours}
+          aria-pressed={index === chosen}
           onClick={() => onChange(range)}
           className={cn(
-            "rounded-full px-2.5 py-1 text-xs transition-colors",
-            range.hours === value.hours
-              ? "bg-accent text-accent-foreground"
+            "relative z-10 min-w-0 rounded-full px-2.5 py-1 text-xs transition-colors",
+            index === chosen
+              ? "text-accent-foreground"
               : "text-muted-foreground hover:bg-accent/50",
           )}
         >