Collapse the strategy, backtest and sweep panels

Adds a reusable CollapsiblePanel (chevron header, optional summary shown when
collapsed, state persisted in localStorage) and wraps the Strategy, Backtest
and Parameter sweep panels with it, so any single part of the dashboard can be
focused on quickly. Panels stay mounted (v-show) so their form/results state is
preserved across collapse. Includes component tests.

frontend/src/components/SweepPanel.vue

@@ -2,6 +2,7 @@
 import { computed, ref, watch } from 'vue'
 import * as api from '../api'
 import { fmtMoney, pnlClass, signed } from '../format'
+import CollapsiblePanel from './CollapsiblePanel.vue'
 
 const props = defineProps({
   strategies: { type: Array, required: true },
@@ -21,6 +22,13 @@ const gridText = ref({})
 
 const selected = computed(() => props.strategies.find((s) => s.key === selectedKey.value))
 
+const summary = computed(() => {
+  if (!result.value) return ''
+  const top = result.value.rows[0]
+  const best = top ? ` · best ${signed(top.metrics.total_return_pct)}%` : ''
+  return `${result.value.combinations} combinations${best}`
+})
+
 watch(
   () => props.strategies,
   (list) => {
@@ -84,14 +92,8 @@ async function run() {
 </script>
 
 <template>
-  <div class="card space-y-3">
-    <div class="flex items-center justify-between">
-      <h2 class="font-semibold">Parameter sweep</h2>
-      <span v-if="result" class="text-xs text-slate-400">
-        {{ result.combinations }} combinations · top {{ result.rows.length }}
-      </span>
-    </div>
-
+  <CollapsiblePanel title="Parameter sweep" storage-key="sweep" :summary="summary">
+    <div class="space-y-3">
     <div class="grid gap-2 sm:grid-cols-4">
       <label class="space-y-1">
         <span class="label">Strategy</span>
@@ -168,5 +170,6 @@ async function run() {
         </tbody>
       </table>
     </div>
-  </div>
+    </div>
+  </CollapsiblePanel>
 </template>