perf: add search debounce and increase global search timeout

- SearchBar: 300ms debounce with local input state, flush on Enter
- CommandPalette: global search debounce 200→400ms
- Show "500+" when search results are capped
- Fix: syncSearchMatchesWithRendered now updates searchMatchItemIds

Ported from upstream 5c7f921e (SearchBar/CommandPalette parts).

src/renderer/components/search/CommandPalette.tsx

@@ -288,7 +288,7 @@ export const CommandPalette = (): React.JSX.Element | null => {
           setLoading(false);
         }
       }
-    }, 200);
+    }, 400);
 
     return () => clearTimeout(timeoutId);
   }, [query, selectedProjectId, commandPaletteOpen, searchMode, globalSearchEnabled]);

src/renderer/components/search/SearchBar.tsx

@@ -1,14 +1,19 @@
 /**
  * SearchBar - In-session search interface component.
  * Appears at the top of the chat view when Cmd+F is pressed.
+ *
+ * Uses a local input state with debouncing to avoid triggering expensive
+ * search on every keystroke.
  */
 
-import { useEffect, useRef } from 'react';
+import { useCallback, useEffect, useRef, useState } from 'react';
 
 import { useStore } from '@renderer/store';
 import { ChevronDown, ChevronUp, X } from 'lucide-react';
 import { useShallow } from 'zustand/react/shallow';
 
+const SEARCH_DEBOUNCE_MS = 300;
+
 interface SearchBarProps {
   tabId?: string;
 }
@@ -19,6 +24,7 @@ export const SearchBar = ({ tabId }: SearchBarProps): React.JSX.Element | null =
     searchVisible,
     searchResultCount,
     currentSearchIndex,
+    searchResultsCapped,
     conversation,
     setSearchQuery,
     hideSearch,
@@ -30,6 +36,7 @@ export const SearchBar = ({ tabId }: SearchBarProps): React.JSX.Element | null =
       searchVisible: s.searchVisible,
       searchResultCount: s.searchResultCount,
       currentSearchIndex: s.currentSearchIndex,
+      searchResultsCapped: s.searchResultsCapped,
       conversation: tabId
         ? (s.tabSessionData[tabId]?.conversation ?? s.conversation)
         : s.conversation,
@@ -40,8 +47,43 @@ export const SearchBar = ({ tabId }: SearchBarProps): React.JSX.Element | null =
     }))
   );
 
+  // Local input value for responsive typing — debounced before triggering search
+  const [localQuery, setLocalQuery] = useState(searchQuery);
+  const debounceRef = useRef<ReturnType<typeof setTimeout>>(
+    0 as unknown as ReturnType<typeof setTimeout>
+  );
+
   const inputRef = useRef<HTMLInputElement>(null);
 
+  // Sync local state when store query changes externally (e.g., hideSearch clears it)
+  useEffect(() => {
+    setLocalQuery(searchQuery);
+  }, [searchQuery]);
+
+  // Debounced search dispatch
+  const handleChange = useCallback(
+    (value: string) => {
+      setLocalQuery(value);
+      clearTimeout(debounceRef.current);
+
+      // Clear immediately when input is emptied
+      if (!value.trim()) {
+        setSearchQuery('', conversation);
+        return;
+      }
+
+      debounceRef.current = setTimeout(() => {
+        setSearchQuery(value, conversation);
+      }, SEARCH_DEBOUNCE_MS);
+    },
+    [conversation, setSearchQuery]
+  );
+
+  // Cleanup timeout on unmount
+  useEffect(() => {
+    return () => clearTimeout(debounceRef.current);
+  }, []);
+
   // Auto-focus input when search becomes visible
   useEffect(() => {
     if (searchVisible && inputRef.current) {
@@ -55,6 +97,11 @@ export const SearchBar = ({ tabId }: SearchBarProps): React.JSX.Element | null =
     if (e.key === 'Escape') {
       hideSearch();
     } else if (e.key === 'Enter') {
+      // Flush any pending debounce immediately on Enter
+      clearTimeout(debounceRef.current);
+      if (localQuery !== searchQuery) {
+        setSearchQuery(localQuery, conversation);
+      }
       if (e.shiftKey) {
         previousSearchResult();
       } else {
@@ -67,14 +114,18 @@ export const SearchBar = ({ tabId }: SearchBarProps): React.JSX.Element | null =
     return null;
   }
 
+  const resultLabel = searchResultsCapped
+    ? `${currentSearchIndex + 1} of ${searchResultCount}+`
+    : `${currentSearchIndex + 1} of ${searchResultCount}`;
+
   return (
     <div className="absolute right-4 top-2 z-20 flex items-center gap-2 rounded-lg border border-border bg-surface px-3 py-2 shadow-lg">
       {/* Search input */}
       <input
         ref={inputRef}
         type="text"
-        value={searchQuery}
-        onChange={(e) => setSearchQuery(e.target.value, conversation)}
+        value={localQuery}
+        onChange={(e) => handleChange(e.target.value)}
         onKeyDown={handleKeyDown}
         placeholder="Find in conversation..."
         className="w-48 rounded border border-border bg-surface-raised px-3 py-1.5 text-sm text-text focus:border-text-secondary focus:outline-none"
@@ -83,9 +134,7 @@ export const SearchBar = ({ tabId }: SearchBarProps): React.JSX.Element | null =
       {/* Result count */}
       {searchQuery && (
         <span className="whitespace-nowrap text-xs text-text-secondary">
-          {searchResultCount > 0
-            ? `${currentSearchIndex + 1} of ${searchResultCount}`
-            : 'No results'}
+          {searchResultCount > 0 ? resultLabel : 'No results'}
         </span>
       )}
 

src/renderer/store/slices/conversationSlice.ts

@@ -397,10 +397,17 @@ export const createConversationSlice: StateCreator<AppState, [], [], Conversatio
       });
     }
 
+    // Rebuild matchItemIds from synced matches
+    const syncedMatchItemIds = new Set<string>();
+    for (const match of nextMatches) {
+      syncedMatchItemIds.add(match.itemId);
+    }
+
     set({
       searchMatches: nextMatches,
       searchResultCount: nextMatches.length,
       currentSearchIndex: newCurrentIndex,
+      searchMatchItemIds: syncedMatchItemIds,
     });
   },