feat(themes): replace cycle button with popover theme picker

Click theme button opens panel grouped by dark/light. Hover previews
theme live, click confirms. Dismiss on outside-click or Escape.

web/app.js

@@ -1892,20 +1892,88 @@
 
   // ========== Theme ==========
 
-  const THEMES = ['dark', 'paper', 'tinycard', 'catppuccin', 'catppuccin-latte', 'nord', 'dracula', 'gruvbox', 'rosepine', 'rosepine-dawn', 'tokyonight', 'solarized', 'solarized-light'];
+  const THEMES_DARK = [
-  const THEME_ICONS = { dark: '◑', paper: '◐', tinycard: '◈', catppuccin: '◕', 'catppuccin-latte': '◔', nord: '◓', dracula: '◒', gruvbox: '◔', rosepine: '◍', 'rosepine-dawn': '◌', tokyonight: '◗', solarized: '◖', 'solarized-light': '◑' };
+    { id: 'dark', label: 'Noir', swatch: '#c8942a' },
+    { id: 'tinycard', label: 'Tinycard', swatch: '#ad8ee6' },
+    { id: 'catppuccin', label: 'Catppuccin', swatch: '#cba6f7' },
+    { id: 'nord', label: 'Nord', swatch: '#88c0d0' },
+    { id: 'dracula', label: 'Dracula', swatch: '#bd93f9' },
+    { id: 'gruvbox', label: 'Gruvbox', swatch: '#fabd2f' },
+    { id: 'rosepine', label: 'Rosé Pine', swatch: '#c4a7e7' },
+    { id: 'tokyonight', label: 'Tokyo Night', swatch: '#7aa2f7' },
+    { id: 'solarized', label: 'Solarized', swatch: '#268bd2' },
+  ];
+  const THEMES_LIGHT = [
+    { id: 'paper', label: 'Paper', swatch: '#8a6018' },
+    { id: 'catppuccin-latte', label: 'Catppuccin Latte', swatch: '#8839ef' },
+    { id: 'rosepine-dawn', label: 'Rosé Pine Dawn', swatch: '#907aa9' },
+    { id: 'solarized-light', label: 'Solarized Light', swatch: '#268bd2' },
+  ];
+  const ALL_THEME_IDS = [...THEMES_DARK, ...THEMES_LIGHT].map(t => t.id);
 
   const themeToggle = $('#theme-toggle');
   let nibTheme = localStorage.getItem('nib:theme') || 'dark';
-  if (!THEMES.includes(nibTheme)) nibTheme = 'dark';
+  if (!ALL_THEME_IDS.includes(nibTheme)) nibTheme = 'dark';
   document.documentElement.setAttribute('data-theme', nibTheme);
-  themeToggle.textContent = THEME_ICONS[nibTheme];
+  themeToggle.textContent = '◑';
 
-  themeToggle.addEventListener('click', () => {
+  const popover = document.createElement('div');
-    nibTheme = THEMES[(THEMES.indexOf(nibTheme) + 1) % THEMES.length];
+  popover.className = 'theme-popover';
+  function buildPopover() {
+    popover.innerHTML = '';
+    const addSection = (label, themes) => {
+      const lbl = document.createElement('div');
+      lbl.className = 'theme-popover-label';
+      lbl.textContent = label;
+      popover.appendChild(lbl);
+      themes.forEach(t => {
+        const item = document.createElement('div');
+        item.className = 'theme-popover-item' + (t.id === nibTheme ? ' active' : '');
+        item.dataset.theme = t.id;
+        item.innerHTML = `<span class="theme-popover-swatch" style="background:${t.swatch}"></span>${t.label}`;
+        popover.appendChild(item);
+      });
+    };
+    addSection('Dark', THEMES_DARK);
+    addSection('Light', THEMES_LIGHT);
+  }
+  buildPopover();
+  themeToggle.appendChild(popover);
+
+  let previewTheme = null;
+  themeToggle.addEventListener('click', (e) => {
+    if (e.target.closest('.theme-popover-item')) return;
+    popover.classList.toggle('open');
+  });
+
+  popover.addEventListener('mouseover', (e) => {
+    const item = e.target.closest('.theme-popover-item');
+    if (!item) return;
+    previewTheme = item.dataset.theme;
+    document.documentElement.setAttribute('data-theme', previewTheme);
+  });
+
+  popover.addEventListener('mouseleave', () => {
+    previewTheme = null;
+    document.documentElement.setAttribute('data-theme', nibTheme);
+  });
+
+  popover.addEventListener('click', (e) => {
+    const item = e.target.closest('.theme-popover-item');
+    if (!item) return;
+    nibTheme = item.dataset.theme;
+    previewTheme = null;
     document.documentElement.setAttribute('data-theme', nibTheme);
     localStorage.setItem('nib:theme', nibTheme);
-    themeToggle.textContent = THEME_ICONS[nibTheme];
+    popover.classList.remove('open');
+    buildPopover();
+  });
+
+  document.addEventListener('click', (e) => {
+    if (!themeToggle.contains(e.target)) popover.classList.remove('open');
+  });
+  document.addEventListener('keydown', (e) => {
+    if (e.key === 'Escape') popover.classList.remove('open');
   });
 
   // ========== Init ==========

web/style.css

@@ -382,6 +382,7 @@ nav { display: flex; gap: 2px; }
 #search-input::placeholder { color: var(--dim); }
 
 .theme-toggle {
+    position: relative;
     margin-left: auto;
     border: 1px solid var(--border);
     border-radius: var(--r1);
@@ -394,6 +395,60 @@ nav { display: flex; gap: 2px; }
 
 .theme-toggle:hover { color: var(--accent); border-color: var(--accent); }
 
+.theme-popover {
+    position: absolute;
+    top: calc(100% + 6px);
+    right: 0;
+    z-index: 900;
+    background: var(--surf);
+    border: 1px solid var(--border);
+    border-radius: var(--r3);
+    padding: 8px 0;
+    min-width: 180px;
+    box-shadow: 0 8px 24px rgba(0,0,0,.3);
+    display: none;
+}
+
+.theme-popover.open { display: block; }
+
+.theme-popover-label {
+    padding: 4px 12px;
+    font-size: 10px;
+    font-family: var(--mono);
+    color: var(--dim);
+    text-transform: uppercase;
+    letter-spacing: .5px;
+}
+
+.theme-popover-item {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    padding: 6px 12px;
+    cursor: pointer;
+    font-size: 13px;
+    font-family: var(--sans);
+    color: var(--muted);
+    transition: background var(--t-fast), color var(--t-fast);
+}
+
+.theme-popover-item:hover {
+    background: var(--a-bg);
+    color: var(--text);
+}
+
+.theme-popover-item.active {
+    color: var(--accent);
+}
+
+.theme-popover-swatch {
+    width: 12px;
+    height: 12px;
+    border-radius: 50%;
+    border: 1px solid var(--border);
+    flex-shrink: 0;
+}
+
 /* ── MAIN LAYOUT ────────────────────────────────────── */
 main {
     display: grid;