feat: Gmail-style keyboard navigation and multi-select for message list

themes/base.css

@@ -245,3 +245,55 @@ html[data-or-fontsize="large"] [role="listbox"],
 html[data-or-fontsize="large"] [role="list"] {
   font-size: 15px !important;
 }
+
+
+/* ============================================================
+   KEYBOARD NAVIGATION
+   ============================================================ */
+
+/* Focus cursor — the message the keyboard is currently pointing at */
+.or-kb-focused {
+  outline: 2px solid var(--or-accent, #0078d4) !important;
+  outline-offset: -2px;
+  position: relative;
+  z-index: 1;
+}
+
+/* Selected/checked messages */
+.or-kb-selected {
+  background-color: rgba(0, 120, 212, 0.08) !important;
+}
+
+html[data-outlook-relook-scheme="dark"] .or-kb-selected {
+  background-color: rgba(100, 181, 246, 0.12) !important;
+}
+
+/* Selection indicator — small left bar */
+.or-kb-selected::before {
+  content: '';
+  position: absolute;
+  left: 0;
+  top: 0;
+  bottom: 0;
+  width: 3px;
+  background: var(--or-accent, #0078d4);
+}
+
+/* Selection count badge (injected by keyboard.js) */
+.or-kb-selection-count {
+  position: fixed;
+  bottom: 16px;
+  left: 50%;
+  transform: translateX(-50%);
+  background: var(--or-bg-primary, #333);
+  color: var(--or-text-primary, #fff);
+  border: 1px solid var(--or-border, #555);
+  padding: 6px 16px;
+  border-radius: 20px;
+  font-size: 13px;
+  font-family: system-ui, sans-serif;
+  z-index: 999998;
+  box-shadow: 0 4px 12px rgba(0,0,0,0.2);
+  pointer-events: none;
+  transition: opacity 0.15s;
+}