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/hooks/use-debounced-value.ts

@@ -0,0 +1,30 @@
+import { useEffect, useState } from "react";
+import { AppData } from "@/src/data/app-data";
+
+type Params<T> = {
+    value: T;
+    delay_ms?: number;
+};
+
+/**
+ * `value` once it has stopped changing for `delay_ms`
+ * (`AppData.SearchDebounceMs` by default), so a search box searches as the
+ * user types without a request per keystroke. An emptied value comes
+ * through at once.
+ */
+export default function useDebouncedValue<T>({ value, delay_ms = AppData.SearchDebounceMs }: Params<T>) {
+    const [debounced, setDebounced] = useState(value);
+
+    useEffect(() => {
+        if (!value) {
+            setDebounced(value);
+            return;
+        }
+
+        const timer = setTimeout(() => setDebounced(value), delay_ms);
+
+        return () => clearTimeout(timer);
+    }, [value, delay_ms]);
+
+    return debounced;
+}