perf(addon-search): cache lowercased line text in line cache

Lazily store a lowercased line variant in the line cache entry to avoid
repeated toLowerCase calls during case-insensitive searches.

Co-authored-by: Cursor <cursoragent@cursor.com>

addons/addon-search/src/SearchEngine.ts

@@ -292,7 +292,17 @@ export class SearchEngine {
     let searchStringLine = stringLine;
     if (!searchOptions.regex) {
       searchTerm = searchOptions.caseSensitive ? term : term.toLowerCase();
-      searchStringLine = searchOptions.caseSensitive ? stringLine : stringLine.toLowerCase();
+      if (searchOptions.caseSensitive) {
+        searchStringLine = stringLine;
+      } else {
+        let lowerLine = cache[2];
+        if (!lowerLine) {
+          lowerLine = stringLine.toLowerCase();
+          cache[2] = lowerLine;
+          this._lineCache.setLineInCache(row, cache);
+        }
+        searchStringLine = lowerLine;
+      }
     }
 
     let resultIndex = -1;

addons/addon-search/src/SearchLineCache.ts

@@ -15,7 +15,11 @@ export type LineCacheEntry = [
   /**
    * The offsets where each line starts when the entry describes a wrapped line.
    */
-  lineOffsets: number[]
+  lineOffsets: number[],
+  /**
+   * Lowercased line text for case-insensitive searches, lazily populated.
+   */
+  lineAsLower?: string
 ];
 
 /**