fix(web): keep health and status live everywhere they are shown

The SSE stream already carried health.changed, health.stale, signal.raised,
signal.resolved and coverage.unmonitored, but two of the places that render
health never listened for them.

- The Fleet table refreshed only on entity.*, so its Health column sat at
  whatever it was when the page mounted while the map view beside it — which
  did listen — updated live. Health arrives on its own events, not entity.*.
  Coalesced on a 400ms timer because health.stale fires once per entity during
  a sweep, and refetching the whole fleet per event would mean a burst of
  identical requests.
- The entity detail window loaded health, signals and monitoring once on open
  and never again, so a window left on screen kept showing the health it had
  at mount. That is the same staleness this whole change set has been about,
  reproduced one window at a time. Now scoped by entity_id, and re-reads only
  what a health or signal event can actually change rather than re-running the
  full 11-request load().

Verified against live prod: flipping lxc:apps healthy -> degraded -> healthy
updated the Fleet table and an open detail window together, without a reload.

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

web/src/pages/KnowledgeBase.svelte

@@ -177,10 +177,28 @@
     return unsubscribe
   })
 
+  // Health arrives on its own events, not entity.*, so the table's Health
+  // column used to sit at whatever it was when the page mounted while the
+  // graph view beside it updated live. Coalesced because health.stale fires
+  // once per entity during a sweep, and refetching the whole fleet for each
+  // would mean a burst of identical requests.
+  let fleetRefresh: ReturnType<typeof setTimeout> | null = null
+  function refreshFleetSoon() {
+    if (fleetRefresh) return
+    fleetRefresh = setTimeout(() => {
+      fleetRefresh = null
+      loadEntities()
+    }, 400)
+  }
+
   $effect(() => {
     const ev = $liveEvents[0]
-    if (!ev || !ev.type.startsWith('entity.')) return
-    loadEntities()
+    if (!ev) return
+    if (ev.type.startsWith('entity.')) {
+      loadEntities()
+      return
+    }
+    if (ev.type === 'health.changed' || ev.type === 'health.stale') refreshFleetSoon()
   })
 
   const filteredEntities = $derived.by(() => {