web: drive control limits from the served bounds and clamp, not 400

The store fetches {config, bounds} at startup and snaps values into
range everywhere they enter: typed fields, sliders, panel overrides,
and shared links (a ?edgesPerNode=150 link now runs at 8 instead of
showing a validation error). Shrinking numStudents pulls numEducated
and origin down with it. If the bounds fetch fails the app still
starts and the engine's validation backstops. Native min/max
attributes follow the same numbers, so spinners stop at the bounds.

web/src/components/ControlsCard.vue

@@ -36,8 +36,8 @@ const offendsNumEducated = computed(
       label="Chance to forward"
       hint="per friendship, per round"
       :value="base.forwardProb"
-      :min="0"
-      :max="1"
+      :min="store.state.bounds?.forwardProb.min ?? 0"
+      :max="store.state.bounds?.forwardProb.max ?? 1"
       :step="0.01"
       :display-value="formatPct(base.forwardProb * 100)"
       :invalid="offendsForwardProb"