fix: keep disabled dialog selects visually disabled

Exclude .t-is-disabled from the select readonly appearance
override so true disabled selects keep TDesign disabled styles.

src/styles/prototype.css

@@ -721,8 +721,8 @@ svg:not(.t-icon){ width: 18px; height: 18px; fill: none; stroke: currentColor; s
 .add-dock-dialog .t-input--focused{ border-color: #6799d1; box-shadow: 0 0 0 3px rgba(31,111,235,.08); }
 .add-dock-dialog .t-input.t-is-readonly, .add-dock-dialog .t-input.t-is-readonly .t-input__inner{ color: #77838d; background: #f2f4f6; cursor: not-allowed; }
 /* Select 内部 input 默认 readonly，但不是禁用；恢复可交互外观 */
-.add-dock-dialog .t-select .t-input.t-is-readonly,
-.add-dock-dialog .t-select .t-input.t-is-readonly .t-input__inner {
+.add-dock-dialog .t-select .t-input.t-is-readonly:not(.t-is-disabled),
+.add-dock-dialog .t-select .t-input.t-is-readonly:not(.t-is-disabled) .t-input__inner {
   color: var(--ink);
   background: #fff;
   cursor: pointer;