feat(desktop): 1s debounce + auto-save search history on collapse

- Increase relay query debounce from 300ms to 1000ms for inline search
  (reduces unnecessary relay load while typing)
- Save query to SearchHistoryStore when search collapses (if non-empty)
- SearchHistoryStore.addToHistory() already deduplicates by serialized query

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/FeedScreen.kt

@@ -828,7 +828,7 @@ private fun FeedTabsHeader(
     val pinnedFeeds by feedRepo.pinnedFeeds.collectAsState()
     val sidePadding = LocalReadingSidePadding.current
     val scope = rememberCoroutineScope()
-    val searchState = remember { AdvancedSearchBarState(scope) }
+    val searchState = remember { AdvancedSearchBarState(scope, debounceMs = 1000L) }
     var searchText by remember { mutableStateOf(TextFieldValue("")) }
     val focusRequester = remember { FocusRequester() }
     val focusManager = LocalFocusManager.current
@@ -841,9 +841,13 @@ private fun FeedTabsHeader(
         searchState.updateFromText(searchText.text)
     }
 
-    // Clear on collapse
+    // Save to history + clear on collapse
     LaunchedEffect(searchExpanded) {
         if (!searchExpanded) {
+            val query = searchState.query.value
+            if (!query.isEmpty) {
+                SearchHistoryStore.addToHistory(query)
+            }
             searchText = TextFieldValue("")
             searchState.clearSearch()
         }