feat(website): Add last updated dates for agents, prompts, instructions, and skills

- Add git-dates.mjs utility to extract file modification dates from git history
- Include lastUpdated field in JSON data for all resource types
- Display relative time (e.g., '3 days ago') with full date on hover
- Add 'Recently Updated' sort option to agents, prompts, instructions, and skills pages
- Update deploy-website.yml to use fetch-depth: 0 for full git history

CI overhead: ~20-30s additional for full git checkout

website/src/scripts/pages/instructions.ts

@@ -3,13 +3,14 @@
  */
 import { createChoices, getChoicesValues, type Choices } from '../choices';
 import { FuzzySearch, SearchItem } from '../search';
-import { fetchData, debounce, escapeHtml, getGitHubUrl, getInstallDropdownHtml, setupDropdownCloseHandlers, getActionButtonsHtml, setupActionHandlers } from '../utils';
+import { fetchData, debounce, escapeHtml, getGitHubUrl, getInstallDropdownHtml, setupDropdownCloseHandlers, getActionButtonsHtml, setupActionHandlers, getLastUpdatedHtml } from '../utils';
 import { setupModal, openFileModal } from '../modal';
 
 interface Instruction extends SearchItem {
   path: string;
   applyTo?: string;
   extensions?: string[];
+  lastUpdated?: string | null;
 }
 
 interface InstructionsData {
@@ -19,11 +20,25 @@ interface InstructionsData {
   };
 }
 
+type SortOption = 'title' | 'lastUpdated';
+
 const resourceType = 'instruction';
 let allItems: Instruction[] = [];
 let search = new FuzzySearch<Instruction>();
 let extensionSelect: Choices;
 let currentFilters = { extensions: [] as string[] };
+let currentSort: SortOption = 'title';
+
+function sortItems(items: Instruction[]): Instruction[] {
+  return [...items].sort((a, b) => {
+    if (currentSort === 'lastUpdated') {
+      const dateA = a.lastUpdated ? new Date(a.lastUpdated).getTime() : 0;
+      const dateB = b.lastUpdated ? new Date(b.lastUpdated).getTime() : 0;
+      return dateB - dateA;
+    }
+    return a.title.localeCompare(b.title);
+  });
+}
 
 function applyFiltersAndRender(): void {
   const searchInput = document.getElementById('search-input') as HTMLInputElement;
@@ -41,6 +56,8 @@ function applyFiltersAndRender(): void {
     });
   }
 
+  results = sortItems(results);
+
   renderItems(results, query);
   let countText = `${results.length} of ${allItems.length} instructions`;
   if (currentFilters.extensions.length > 0) {
@@ -67,6 +84,7 @@ function renderItems(items: Instruction[], query = ''): void {
           ${item.applyTo ? `<span class="resource-tag">applies to: ${escapeHtml(item.applyTo)}</span>` : ''}
           ${item.extensions?.slice(0, 4).map(e => `<span class="resource-tag tag-extension">${escapeHtml(e)}</span>`).join('') || ''}
           ${item.extensions && item.extensions.length > 4 ? `<span class="resource-tag">+${item.extensions.length - 4} more</span>` : ''}
+          ${getLastUpdatedHtml(item.lastUpdated)}
         </div>
       </div>
       <div class="resource-actions">
@@ -92,6 +110,7 @@ export async function initInstructionsPage(): Promise<void> {
   const list = document.getElementById('resource-list');
   const searchInput = document.getElementById('search-input') as HTMLInputElement;
   const clearFiltersBtn = document.getElementById('clear-filters');
+  const sortSelect = document.getElementById('sort-select') as HTMLSelectElement;
 
   const data = await fetchData<InstructionsData>('instructions.json');
   if (!data || !data.items) {
@@ -109,13 +128,20 @@ export async function initInstructionsPage(): Promise<void> {
     applyFiltersAndRender();
   });
 
+  sortSelect?.addEventListener('change', () => {
+    currentSort = sortSelect.value as SortOption;
+    applyFiltersAndRender();
+  });
+
   applyFiltersAndRender();
   searchInput?.addEventListener('input', debounce(() => applyFiltersAndRender(), 200));
 
   clearFiltersBtn?.addEventListener('click', () => {
     currentFilters = { extensions: [] };
+    currentSort = 'title';
     extensionSelect.removeActiveItems();
     if (searchInput) searchInput.value = '';
+    if (sortSelect) sortSelect.value = 'title';
     applyFiltersAndRender();
   });