Fold the brain and health screens into Home

Home is the one overview now: the brain graph flat across the top, the flow
switches, then the health sections. The /brain and /health routes and their
sidebar entries are gone.

- charts report their cursor and clicks, so hovering one filters the list
  beside it to that minute and a click pins it until Escape or Clear
- chart values round to about three significant digits, the legend mounts
  under the plot so it can wrap without leaving the card, and axis ticks
  shorten past a thousand
- the embedded brain leaves the wheel to the page rather than zooming
- number fields no longer draw their up/down spinner (NOTEPAD)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017MeiWk3Yq12n2pTvnQWYvt

NOTEPAD.md

@@ -15,7 +15,6 @@ should reopen it.
 
 - INFRA: merge the philosophy statement at the beginning of vision.md into the rest of the document. Dissolve the decision dates and fold the decisions into a clean structure
 - BUG/UI mobile friendly support is degraded: 1) toolbar in the "Flows" viewport extend mobile viewport width 2) position of nodes should never be static; always adjust such that there are as few as possible overlaps (of nodes and edge labels) and direction is left to right (desktop) or top to bottom (mobile) with a minimal (but clean) overall edge length 3) Dashboard view is not mobile friendly at all; as dashboard design is infeasible on mobile, render all widgets in a vertically stacked order. This allows to inspect each widget and make changes. Layout changes are not a feature on mobile 4) the home view is not responsive; all items shown there should re-order on mobile such that no scrollbars appear
-- BUG/UI remove the up/down counters from integer fields (global)
 
 ### Connector write paths
 
@@ -52,6 +51,7 @@ is what M4 still waits on, together with porting the flows.
 - CHORE/API: the metrics collector is a bus subscriber, so a storm that overflows the bus queue undercounts. The events dropped are the same ones the websocket drops; exact accounting would need the collector to be fed from the engine rather than the bus.
 - CHORE/API: `/observability/summary` reports the work queue's `depth` as the Redis stream length, which is the journal size (capped at `STREAM_MAXLEN`) rather than a backlog. The health screen shows `pending` instead; the field name still invites the wrong reading.
 - FEAT/UI: the health screen's window is fixed at 24 hours and the charts fold minute buckets in Python. A range picker (and `date_bin()` behind it) is the next step if anyone wants a week.
+- FEAT/API: `/observability/runs` takes no time range and caps at 200 rows, so picking a minute on the throughput chart can only filter the runs the list happens to hold — on a busy engine that is its last minute or so, and any earlier minute reads as empty. A `since`/`until` parameter would let a moment on a chart reach the whole day. Failures are sparse enough that the same pairing works there.
 - CHORE/FLOW: run records for a deleted flow stay until the retention window passes, so a flow that no longer exists keeps appearing in the history. Deliberate — it is a record of what ran — but `forget_flow` could offer to clear it.
 - CHORE/API: nothing can ask the collector to flush now, so anything needing the tables to be current has to wait out `FLUSH_INTERVAL_S` — which is what the soak harness does before clearing its own rows.
 - BUG/UI: `MemoryWorkQueue.stats()` hard-codes `pending: 0`, so the health tile always reads zero on a stack without Redis.
@@ -85,6 +85,7 @@ is what M4 still waits on, together with porting the flows.
 - CHORE/UX: the derived-cron chip also appears on the delay node, where `interval` is a rate limit rather than a schedule. May want it inject-only.
 - CHORE/UX: free-form params (python nodes) get no suggestions, since there is no schema to key them off.
 - PERF/UI: `BrainView` runs 300 force-layout ticks synchronously inside a `useMemo`, so the graph is laid out on the render thread.
+- FEAT/UI: the brain is a band on a scrolling page now, so it neither pans nor zooms — the fit keeps the whole graph in view instead. An installation with enough flows to make the labels unreadable at that fit needs a way to open the graph larger.
 - FEAT/UI: the brain graph draws connections as plain lines, so which way a value travels is not shown. An arrowhead needs the path shortened to the target circle's rim, which needs the node radius on the edge.
 - CHORE/UI: fixing the yellow message pulse gave `edge-pulse` an explicit `to`, so a *selected* edge now decays to `--muted-foreground` and snaps back to its blue at the end instead of decaying into it. Barely visible, and only while an edge is selected.