Fix Codex OAuth configuration and refine UI controls

src/styles.css

@@ -440,71 +440,40 @@ input:focus-visible {
   border-top: 1px solid var(--theme-e3e1db);
 }
 
-.sidebar-theme-toggle {
+.sidebar-theme-selector {
   display: grid;
-  grid-template-columns: 18px minmax(0, 1fr) 36px;
-  align-items: center;
-  gap: 8px;
+  grid-template-columns: repeat(2, minmax(0, 1fr));
+  gap: 3px;
   width: 100%;
-  min-height: 40px;
-  padding: 0 10px;
+  padding: 3px;
   border: 1px solid var(--theme-d8d4cc);
   border-radius: 8px;
   background: var(--theme-fffdf8);
-  color: var(--theme-716b61);
-  text-align: left;
 }
 
-.sidebar-theme-toggle:hover {
-  border-color: var(--theme-c7c2b8);
+.sidebar-theme-selector button {
+  min-width: 0;
+  min-height: 32px;
+  padding: 0 8px;
+  border: 0;
+  border-radius: 5px;
+  background: transparent;
+  color: var(--theme-716b61);
+  font-size: 12px;
+  font-weight: 700;
+  transition: background 140ms ease, color 140ms ease, box-shadow 140ms ease;
+  white-space: nowrap;
+}
+
+.sidebar-theme-selector button:hover {
   background: var(--theme-e8e5dc);
   color: var(--theme-2d2a26);
 }
 
-.sidebar-theme-toggle > svg {
-  color: var(--theme-7a746c);
-}
-
-.sidebar-theme-toggle > span {
-  min-width: 0;
-  overflow: hidden;
-  font-size: 12px;
-  font-weight: 700;
-  text-overflow: ellipsis;
-  white-space: nowrap;
-}
-
-.theme-switch-track {
-  position: relative;
-  display: block;
-  width: 36px;
-  height: 20px;
-  border: 1px solid var(--theme-c7c2b8);
-  border-radius: 999px;
+.sidebar-theme-selector button.active {
   background: var(--theme-dfdcd4);
-  transition: border-color 160ms ease, background 160ms ease;
-}
-
-.theme-switch-track b {
-  position: absolute;
-  top: 2px;
-  left: 2px;
-  display: block;
-  width: 14px;
-  height: 14px;
-  border-radius: 50%;
-  background: var(--theme-fff);
-  box-shadow: 0 1px 3px rgba(45, 42, 38, 0.24);
-  transition: transform 180ms ease, background 160ms ease;
-}
-
-.sidebar-theme-toggle[aria-pressed='true'] .theme-switch-track {
-  border-color: var(--theme-8069ad);
-  background: var(--theme-654f91);
-}
-
-.sidebar-theme-toggle[aria-pressed='true'] .theme-switch-track b {
-  transform: translateX(16px);
+  box-shadow: inset 0 0 0 1px var(--theme-d5d2cb);
+  color: var(--theme-2d2a26);
 }
 
 .sidebar-language {