fix (tui): keep assistant text contrast theme-adaptive

src/tui/components/assistant-message.ts

@@ -7,7 +7,9 @@ export class AssistantMessageComponent extends Container {
   constructor(text: string) {
     super();
     this.body = new Markdown(text, 1, 0, markdownTheme, {
-      color: (line) => theme.fg(line),
+      // Keep assistant body text in terminal default foreground so contrast
+      // follows the user's terminal theme (dark or light).
+      color: (line) => theme.assistantText(line),
     });
     this.addChild(new Spacer(1));
     this.addChild(this.body);

src/tui/theme/theme.ts

@@ -61,6 +61,7 @@ function highlightCode(code: string, lang?: string): string[] {
 
 export const theme = {
   fg: fg(palette.text),
+  assistantText: (text: string) => text,
   dim: fg(palette.dim),
   accent: fg(palette.accent),
   accentSoft: fg(palette.accentSoft),