fix(webui): ARIA-valid hover text, alias metadata guard, context-chip polish

CompactNumber.vue and ProviderRateBadge.vue both put aria-label on a
plain <span> — axe's aria-prohibited-attr rule: a <span>'s implicit
ARIA role ("generic") does not support accessible-name computation at
all, so the attribute was simply invalid there, not just discouraged.
Both now use the visible-text-hidden-plus-sr-only-full-text pattern
instead: the compact/label text is marked aria-hidden="true", and a
sr-only sibling span carries the exact value/detail for assistive tech.
title stays on the outer element for mouse hover, unchanged. Folded
review minor.

ProvidersView.vue: the alias table's ModelChip cell read
row.original.modelMeta.contextTokens without a guard, unlike the
provider path's own modelMetaFor fallback — a response from a server
build older than this field (version skew) would throw instead of just
omitting the hover detail. Now optional-chained to match. The visible
context chip beside each model gains title="context window" and
text-xs (was an arbitrary text-[10px]), matching the rest of the panel's
muted-label sizing convention. Folded review minors.

webui/src/components/CompactNumber.vue

@@ -5,13 +5,22 @@ import { formatCompactCount, formatExactInt } from '@/lib/format'
 
 /**
  * CompactNumber renders a large raw token/request count in its compact
- * SI-style form ("1.23M") while carrying the exact value via both
- * `title` (mouse hover) and `aria-label` (keyboard/screen-reader parity
- * — the same established pattern ProviderRateBadge.vue and ModelChip.vue
- * already apply to their own hover detail). Used anywhere a usage count
- * renders: DataTable numeric columns (usage-columns.ts, target-
- * columns.ts, via `h(CompactNumber, { value })`), the Usage tab's Total
- * card, and a group accordion's trigger/detail stat grid (UsageView.vue).
+ * SI-style form ("1.23M") while carrying the exact value via `title`
+ * (mouse hover) and a visually-hidden sibling span (keyboard/screen-
+ * reader parity). Used anywhere a usage count renders: DataTable numeric
+ * columns (usage-columns.ts, target-columns.ts, via
+ * `h(CompactNumber, { value })`), the Usage tab's Total card, and a
+ * group accordion's trigger/detail stat grid (UsageView.vue).
+ *
+ * Review fix (folded minor, ARIA): `aria-label` on a plain `<span>` is
+ * an axe `aria-prohibited-attr` violation — a `<span>`'s implicit ARIA
+ * role ("generic") does not support name computation at all, so
+ * `aria-label`/`aria-labelledby` there is simply invalid, not merely
+ * discouraged. The visible, compact text is marked `aria-hidden="true"`
+ * so assistive tech skips the abbreviated form, and a `sr-only` sibling
+ * span (visually hidden, still in the accessibility tree) carries the
+ * exact value instead — the same visible-abbreviation-plus-hidden-full-
+ * text pattern ProviderRateBadge.vue now applies too.
  *
  * Cost figures are NOT this component's concern — formatCost already
  * shows full 4-decimal precision, so there is nothing to compact or
@@ -24,5 +33,8 @@ const exact = computed(() => formatExactInt(props.value))
 </script>
 
 <template>
-  <span :title="exact" :aria-label="exact">{{ compact }}</span>
+  <span :title="exact">
+    <span aria-hidden="true">{{ compact }}</span>
+    <span class="sr-only">{{ exact }}</span>
+  </span>
 </template>

webui/src/components/ProviderRateBadge.vue

@@ -37,10 +37,16 @@ const label = computed(() => (status.value === 'no-traffic' ? 'no traffic' : for
  * detail carries the "right now" (provider) or "today" (model) counts —
  * the spec's minute-window requirement where that data exists at all
  * (minuteRateTitle), falling back to dayRateTitle when it does not. Used
- * as BOTH the badge's title (mouse hover) and its aria-label (folded
- * review minor, v0.22 review round: title alone is mouse-only — a
- * keyboard or screen-reader user gets none of it without an aria-label
- * carrying the same sentence).
+ * as BOTH the badge's title (mouse hover) and, via the sr-only span in
+ * the template, its accessible name for keyboard/screen-reader users
+ * (folded review minor, v0.22 review round: title alone is mouse-only).
+ *
+ * Review fix (v0.23 round): this used to sit directly on `:aria-label`
+ * on the Badge/`<span>` element, which axe flags as `aria-prohibited-
+ * attr` — a `<span>`'s implicit role ("generic") does not support name
+ * computation. See CompactNumber.vue's own doc comment for the identical
+ * fix and the shared visible-abbreviation-plus-sr-only-full-text
+ * pattern this component now uses too.
  */
 const detail = computed(() =>
   props.attemptsMinute === undefined || props.failuresMinute === undefined
@@ -68,7 +74,8 @@ const extraClass = computed(() => {
 </script>
 
 <template>
-  <Badge as="span" :variant="variant" :class="extraClass" class="font-normal tabular-nums" :title="detail" :aria-label="detail">
-    {{ label }}
+  <Badge as="span" :variant="variant" :class="extraClass" class="font-normal tabular-nums" :title="detail">
+    <span aria-hidden="true">{{ label }}</span>
+    <span class="sr-only">{{ detail }}</span>
   </Badge>
 </template>

webui/src/components/ProvidersView.vue

@@ -179,12 +179,18 @@ const aliasColumns: ColumnDef<AdminAliasView, unknown>[] = [
     id: 'alias',
     header: 'Alias',
     accessorFn: (a) => a.alias,
+    // Optional-chained (review fix, folded minor) the same way
+    // modelMetaFor guards the provider path below: AdminAliasView.
+    // modelMeta is typed as always-present, but a real response from a
+    // server build older than this field (version skew) would otherwise
+    // throw on `.modelMeta.contextTokens` here instead of just omitting
+    // the hover detail.
     cell: ({ row }) =>
       h(ModelChip, {
         id: row.original.alias,
-        contextTokens: row.original.modelMeta.contextTokens,
-        inputPerMTokUsd: row.original.modelMeta.inputPerMTokUsd,
-        outputPerMTokUsd: row.original.modelMeta.outputPerMTokUsd,
+        contextTokens: row.original.modelMeta?.contextTokens,
+        inputPerMTokUsd: row.original.modelMeta?.inputPerMTokUsd,
+        outputPerMTokUsd: row.original.modelMeta?.outputPerMTokUsd,
       }),
   },
   {
@@ -331,7 +337,8 @@ const aliasEmptyMessage = computed(() =>
                   -->
                   <span
                     v-if="modelMetaFor(p, m).contextTokens !== undefined"
-                    class="text-[10px] text-muted-foreground tabular-nums"
+                    title="context window"
+                    class="text-xs text-muted-foreground tabular-nums"
                   >
                     {{ formatContextWindow(modelMetaFor(p, m).contextTokens as number) }}
                   </span>