Search files as the user types

The Files page and the conversation's files modal searched only on
Enter. Both now search by name or path a moment after the last
keystroke (useDebouncedValue, AppData.SearchDebounceMs), clearing shows
the whole list at once, and the modal drops an answer a newer request
overtook. The Files search box no longer locks while a folder loads.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/data/app-data.ts

@@ -688,6 +688,11 @@ export const AppData = {
     RagTopChunks: 8,
     RagOverFetch: 4,
     RagMaxK: 60,
+    /**
+     * How long a search box waits after the last keystroke before it
+     * searches.
+     */
+    SearchDebounceMs: 250,
     /**
      * The database is vacuumed at boot once this share of its pages, and
      * at least this many bytes, sit free (after a big delete, such as the