refactor(ui): 优化 PromptInput 组件中 showFooterText 的计算逻辑

- 将 showFooterText 的 useMemo 提取到统一位置
- 添加 showThemeDropdown 到依赖列表和条件判断
- 移除重复声明的 showFooterText 常量
- 保持相关依赖和逻辑清晰易维护

Author: hqwlkj

src/ui/views/PromptInput.tsx

@@ -214,9 +214,16 @@ export const PromptInput = React.memo(function PromptInput({
         ? `${loadingText}${processOrPasteHint}`
         : `esc to interrupt · ctrl+c to cancel input${processOrPasteHint}`
       : `enter send · shift+enter newline · @ files · ctrl+v image · / commands · ctrl+d exit${processOrPasteHint}`;
+
   const showFooterText = useMemo(
-    () => showMenu || showSkillsDropdown || openRawModelDropdown || showModelDropdown || showFileMentionMenu,
-    [showMenu, showSkillsDropdown, showModelDropdown, openRawModelDropdown, showFileMentionMenu]
+    () =>
+      showMenu ||
+      showSkillsDropdown ||
+      openRawModelDropdown ||
+      showModelDropdown ||
+      showThemeDropdown ||
+      showFileMentionMenu,
+    [showMenu, showSkillsDropdown, showModelDropdown, openRawModelDropdown, showThemeDropdown, showFileMentionMenu]
   );
   const cursorPlacement = useMemo(
     () => getPromptCursorPlacement(buffer, screenWidth, 2, footerText),
@@ -746,17 +753,6 @@ export const PromptInput = React.memo(function PromptInput({
     clearUndoRedoStacks();
   }
 
-  const showFooterText = useMemo(
-    () =>
-      showMenu ||
-      showSkillsDropdown ||
-      openRawModelDropdown ||
-      showModelDropdown ||
-      showThemeDropdown ||
-      showFileMentionMenu,
-    [showMenu, showSkillsDropdown, showModelDropdown, openRawModelDropdown, showThemeDropdown, showFileMentionMenu]
-  );
-
   const isFocused = useMemo(() => !disabled && hasTerminalFocus, [disabled, hasTerminalFocus]);
 
   const matchedCommand = slashToken ? findExactSlashCommand(slashItems, slashToken) : null;