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/components/RepoFileSearch.vue

@@ -5,7 +5,7 @@ import {GET} from '../modules/fetch.ts';
 import {filterRepoFilesWeighted} from '../features/repo-findfile.ts';
 import {pathEscapeSegments} from '../utils/url.ts';
 import {SvgIcon} from '../svg.ts';
-import {throttle} from 'throttle-debounce';
+import {throttle} from '../utils/func.ts';
 
 const props = defineProps({
   repoLink: { type: String, required: true },
@@ -31,10 +31,10 @@ const filteredFiles = computed(() => {
   return filterRepoFilesWeighted(allFiles.value, searchQuery.value);
 });
 
-const applySearchQuery = throttle(300, () => {
+const applySearchQuery = throttle(() => {
   searchQuery.value = refElemInput.value.value;
   selectedIndex.value = 0;
-});
+}, 300);
 
 const handleSearchInput = () => {
   loadFileListForSearch();