refactor: replace debounce/throttle deps with first-party code (#38610)

Adds `web_src/js/utils/func.ts` with `debounce` and `throttle`, dropping
`throttle-debounce` and `perfect-debounce` dependencies. Both were
needed before: the former has no promise-returning debounce, which
`TextExpander` requires, and the latter no `throttle`.

Signature follows lodash and es-toolkit: `(func, wait, {leading,
trailing})` plus `cancel`, so argument order flips at the migrated call
sites.

web_src/js/modules/search.ts

@@ -1,4 +1,4 @@
-import {debounce} from 'throttle-debounce';
+import {debounce} from '../utils/func.ts';
 import {GET} from './fetch.ts';
 import {errorName} from './errors.ts';
 import {html, htmlRaw} from '../utils/html.ts';
@@ -69,7 +69,7 @@ export function attachSearchBox<T = unknown>(container: HTMLElement, url: string
     hide();
   };
 
-  const search = debounce(200, async (query: string) => {
+  const search = debounce(async (query: string) => {
     fetchController?.abort();
     if (query.length < minCharacters) return hide();
     const ctrl = (fetchController = new AbortController());
@@ -82,7 +82,7 @@ export function attachSearchBox<T = unknown>(container: HTMLElement, url: string
     } catch (err) {
       if (errorName(err) !== 'AbortError') hide();
     }
-  });
+  }, 200);
   // cancel + hide ensures a debounced fetch scheduled before any of these can't fire afterwards
   const dismiss = () => { search.cancel(); hide() };