feat: visually group settings by category with collapsible cards

- Each command category (Better Formatting, Line Operations, etc.) now
  renders as a collapsible <details> card with a bordered/shaded header
  showing an 'N/M enabled' badge, instead of a flat list separated only
  by bold text headings.
- Sentence regex + reset moved into the Sentence Navigator category
  card (it configures that category's commands, so it belongs there
  instead of the general section).
- Bulk actions (global enable/disable all, per-category toggle-all,
  regex reset) now patch the DOM in place instead of calling the full
  display() re-render, so open/closed category state is never lost
  when a setting changes.
- Removed the 'General' settings heading (obsidianmd/settings-tab/no-problematic-settings-headings
  lint rule flags it).
- styles.css adds .bindthem-category-* rules for the card borders,
  header shading, collapse caret, and setting-row separators.

styles.css

@@ -1,8 +1,72 @@
-/*
-
-This CSS file will be included with your plugin, and
-available in the app when your plugin is enabled.
-
-If your plugin does not need CSS, delete this file.
-
-*/
+/*
+
+This CSS file will be included with your plugin, and
+available in the app when your plugin is enabled.
+
+*/
+
+/* ============================================================
+   Settings tab — command category grouping
+   ============================================================ */
+
+.bindthem-category-list {
+	margin-bottom: 0.5em;
+}
+
+.bindthem-category {
+	border: 1px solid var(--background-modifier-border);
+	border-radius: var(--radius-m);
+	margin-bottom: 0.5em;
+	overflow: hidden;
+}
+
+.bindthem-category > summary {
+	display: flex;
+	align-items: center;
+	justify-content: space-between;
+	gap: 0.75em;
+	padding: 0.65em 1em;
+	cursor: pointer;
+	font-weight: 600;
+	background-color: var(--background-secondary);
+	list-style: none;
+}
+
+.bindthem-category > summary::-webkit-details-marker {
+	display: none;
+}
+
+.bindthem-category > summary::before {
+	content: '▸';
+	display: inline-block;
+	margin-right: 0.5em;
+	color: var(--text-muted);
+	transition: transform 0.15s ease-in-out;
+}
+
+.bindthem-category[open] > summary::before {
+	transform: rotate(90deg);
+}
+
+.bindthem-category-name {
+	flex: 1;
+}
+
+.bindthem-category-count {
+	font-weight: 400;
+	font-size: var(--font-ui-smaller);
+	color: var(--text-muted);
+	white-space: nowrap;
+}
+
+.bindthem-category-content {
+	padding: 0 1em;
+}
+
+.bindthem-category-content .setting-item {
+	border-top: 1px solid var(--background-modifier-border);
+}
+
+.bindthem-category-content .setting-item:first-child {
+	border-top: none;
+}