Home: one time range across the health block, and failures that follow it

The health screen was fixed at 24 hours everywhere except its lists, which
were fixed at nothing: `failuresQueryOptions` read the newest 100 rows and
`HealthActivity` filtered them client-side, so on a busy engine the failures
list covered whatever few minutes 100 rows happened to span while the chart
beside it spanned a day — and pinning an older minute showed an empty card.

One `RangePicker` now sits on the Health heading and governs the whole block:
the tiles, the flow table, both charts and both lists. Presets are 1h / 6h /
24h / 7d — the collector prunes at `OBS_RETENTION_DAYS` (30), so a week is
behind the last one. The longer windows ask for coarser buckets, since a week
of minute rollups is ten thousand points nobody can see.

Failures get the escape hatch the runs already had: a pinned minute is asked
for with `since`/`until` rather than filtered out of what is held, and the
list itself is bound to the selected range. `RUN_DEPTH`/`EVENT_DEPTH` become
one `LIST_DEPTH`, which now buys coverage of the window on screen instead of
a fixed newest-N — narrowing the range is what makes the same rows reach the
whole of it. The "Failures (24h)" tile counts errors over the selected window
from the rollups the table is drawn from, so tile, column and chart agree.

The node-panel and edge trend curves get no picker. They are a Redis ring of
the last 120 values per message with no window to ask for, so hovering one
reveals what it actually shows — how many readings, and the span they cover.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XC2jX6Hdj7pxGGKzBTrbqB

frontend/src/routes/_layout/index.tsx

@@ -1,8 +1,10 @@
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query"
 import { createFileRoute, Link } from "@tanstack/react-router"
 import { AlertCircle, Workflow } from "lucide-react"
+import { useState } from "react"
 
 import { type FlowSummary, FlowsService } from "@/client"
+import { DEFAULT_RANGE } from "@/components/Common/RangePicker"
 import { BrainView } from "@/components/Flow/BrainView"
 import { flowKeys, flowsQueryOptions } from "@/components/Flow/queries"
 import { HealthActivity } from "@/components/Health/HealthActivity"
@@ -100,6 +102,9 @@ function FlowRow({ flow }: { flow: FlowSummary }) {
  */
 function Dashboard() {
   const { user: currentUser } = useAuth()
+  // The health block's window: one choice, read by the tiles, the flow table,
+  // the charts and the lists under them.
+  const [range, setRange] = useState(DEFAULT_RANGE)
   const { data, isPending } = useQuery({
     ...flowsQueryOptions(),
     refetchInterval: REFRESH_INTERVAL,
@@ -146,8 +151,8 @@ function Dashboard() {
         )}
       </Card>
 
-      <HealthOverview />
-      <HealthActivity />
+      <HealthOverview range={range} onRangeChange={setRange} />
+      <HealthActivity range={range} />
     </div>
   )
 }