Update tab UI, presets interactions, and help

Refine tab presets selection and editing, add per-tab removal, improve layout, and provide an in-app help modal.

src/static/help.js

@@ -0,0 +1,27 @@
+document.addEventListener('DOMContentLoaded', () => {
+  const helpBtn = document.getElementById('help-btn');
+  const helpModal = document.getElementById('help-modal');
+  const helpCloseBtn = document.getElementById('help-close-btn');
+
+  if (helpBtn && helpModal) {
+    helpBtn.addEventListener('click', () => {
+      helpModal.classList.add('active');
+    });
+  }
+
+  if (helpCloseBtn && helpModal) {
+    helpCloseBtn.addEventListener('click', () => {
+      helpModal.classList.remove('active');
+    });
+  }
+
+  if (helpModal) {
+    helpModal.addEventListener('click', (event) => {
+      if (event.target === helpModal) {
+        helpModal.classList.remove('active');
+      }
+    });
+  }
+}
+)
+