fixes: tag assign stale body, board placeholder, plugin pending, bucket activate

- Context menu tag toggle reads fresh body from state.cards — was
  overwriting with stale snapshot, dropping existing tags (e.g. #done)
- Board empty-state centered with flex (vertical + horizontal)
- Plugin settings: batch toggles via Apply button, single reload
  instead of one reload per toggle
- New bucket creation activates it directly on the board

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

public/js/modules/board.js

@@ -584,8 +584,10 @@ export function renderBoard() {
     renderGroupBar(cards);
 
     if (!cards.length) {
-        board.style.display = '';
-        board.innerHTML = `<div class="col-span-full text-center py-20">
+        board.style.display = 'flex';
+        board.style.alignItems = 'center';
+        board.style.justifyContent = 'center';
+        board.innerHTML = `<div class="flex flex-col items-center text-center">
             <i class="ph ph-cards text-4xl text-t-dim mb-4 block"></i>
             <p class="font-pixel text-sm text-t-dim cursor-blink">no cards found</p></div>`;
         const fc = $('footer-count');
@@ -707,6 +709,8 @@ export function renderBoard() {
     }
 
     board.style.display = '';
+    board.style.alignItems = '';
+    board.style.justifyContent = '';
     board.innerHTML = cards.map(c => renderCardHtml(c, inGroup, recent)).join('');
 
     bindCardEvents();