Retry the strategy list and make collapse obvious

- The strategy/preset lists were loaded once with failures swallowed, so a
  single failed first request left the strategy dropdown empty forever. They
  are now retried every 3s until populated.
- Clearer collapse affordance: hover highlight, a hide/show hint, and a
  tooltip; Backtest and Parameter sweep start collapsed so the strategy
  selector and status are immediately visible.
- Adds an integration test that the strategy dropdown is populated and the
  panel actually collapses.

frontend/src/App.vue

@@ -55,6 +55,7 @@ let socket
 let pollTimer
 let statusTimer
 let graceTimer
+let listTimer
 
 async function refreshAll() {
   const [p, o, e, q] = await Promise.all([
@@ -183,11 +184,15 @@ onMounted(() => {
     if (!connected.value) pollingFallback.value = true
   }, 6000)
 
-  // Initial loads are best-effort; the intervals below keep retrying.
+  // Initial loads are best-effort.
   api.getStatus().then((s) => (status.value = s)).catch(() => {})
   refreshAll().catch(() => {})
-  loadStrategies().catch(() => {})
-  loadPresets().catch(() => {})
+
+  // The strategy list and presets rarely change, so load them once but keep
+  // retrying until they arrive: a single failed first request used to leave the
+  // strategy dropdown empty forever.
+  loadStrategies()
+  loadPresets()
 
   // Poll fast enough that the UI feels live even when it is the only channel.
   pollTimer = setInterval(() => refreshAll().catch(() => {}), 3000)
@@ -195,12 +200,20 @@ onMounted(() => {
     () => api.getStatus().then((s) => (status.value = s)).catch(() => {}),
     3000,
   )
+  // Retry the static lists until non-empty (covers a failed first load and a
+  // backend that was still starting up).
+  listTimer = setInterval(() => {
+    if (!strategies.value.length) loadStrategies()
+    if (!presets.value.length) loadPresets()
+    if (strategies.value.length && presets.value.length) clearInterval(listTimer)
+  }, 3000)
 })
 
 onUnmounted(() => {
   socket?.close()
   clearInterval(pollTimer)
   clearInterval(statusTimer)
+  clearInterval(listTimer)
   clearTimeout(graceTimer)
 })
 </script>