tui: simplify mode toggle icon styling

Use consistent strong color for active mode icons instead of different
colors for shell vs normal mode, making the active state more visually
clear to users.

packages/app/src/components/prompt-input.tsx

@@ -1375,8 +1375,7 @@ export const PromptInput: Component<PromptInputProps> = (props) => {
                       name={mode === "shell" ? "console" : "prompt"}
                       class="size-[18px]"
                       classList={{
-                        "text-icon-strong-base": mode === "shell" && store.mode === "shell",
-                        "text-icon-interactive-base": mode === "normal" && store.mode === "normal",
+                        "text-icon-strong-base": store.mode === mode,
                         "text-icon-weak": store.mode !== mode,
                       }}
                     />