fix(dashboard): inline cpu sparkline, history graph host label + stable y-axis

- Hosts-Overview: move the CPU sparkline inline next to the cpu % value it
  represents (was floated far right on the name line, reading as unrelated).
- Host Agent history widget: caption the chart with the host it represents
  (the panel title is generic) — links to the host hub.
- History widget: snap the y-axis to a stable 0..next-10%-band ceiling instead
  of auto-scaling to the exact peak, so the 'zoom' no longer jumps each poll.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/host_agent/routes.py

@@ -465,8 +465,16 @@ async def widget_history():
     # hundreds–thousands of points — a noisy, unreadable line. Bucket-average to a
     # readable point count, keeping the shape.
     series = {k: _downsample(v) for k, v in series.items()}
+
+    # Stable y-axis ceiling. All three series are percentages, so snap the top up
+    # to the next 10% band (floor 20, cap 100). Auto-scaling to the exact peak made
+    # the chart "zoom" jump on every poll as the peak drifted a few %; snapping to
+    # a band keeps the axis steady across refreshes while still filling the panel.
+    peak = max((p[1] for s in series.values() for p in s), default=0.0)
+    y_max = min(100, max(20, ((int(peak) // 10) + 1) * 10))
     return await render_template(
         "widget_history.html", host=host, series=series, hours=hours, wid=wid,
+        y_max=y_max,
     )