fix(frontend): preserve ansi colors in terminal effects

Limit stroke and shadow effects to default-foreground terminal text so
ANSI-colored output keeps its intended visual meaning.

Also enable terminal text stroke and shadow by default in frontend and
backend fallbacks, and align the dark preset and default xterm theme
with the new green night palette.

packages/backend/src/config/default-themes.ts

@@ -3,26 +3,26 @@ import type { ITheme } from 'xterm';
 // 默认 xterm 主题
 // (与 backend/src/config/default-themes.ts 中的定义保持一致)
 export const defaultXtermTheme: ITheme = {
-  background: '#1e1e1e',
-  foreground: '#d4d4d4',
-  cursor: '#d4d4d4',
-  selectionBackground: '#264f78',
-  black: '#000000',
-  red: '#cd3131',
-  green: '#0dbc79',
-  yellow: '#e5e510',
-  blue: '#2472c8',
-  magenta: '#bc3fbc',
-  cyan: '#11a8cd',
-  white: '#e5e5e5',
-  brightBlack: '#666666',
-  brightRed: '#f14c4c',
-  brightGreen: '#23d18b',
-  brightYellow: '#f5f543',
-  brightBlue: '#3b8eea',
-  brightMagenta: '#d670d6',
-  brightCyan: '#29b8db',
-  brightWhite: '#e5e5e5'
+  background: '#111411',
+  foreground: '#d8e6d2',
+  cursor: '#8ff7a7',
+  selectionBackground: '#21462b',
+  black: '#111411',
+  red: '#d96c5f',
+  green: '#59d971',
+  yellow: '#d8ba52',
+  blue: '#4ca89f',
+  magenta: '#6f8f8a',
+  cyan: '#4ec9b0',
+  white: '#d8e6d2',
+  brightBlack: '#5d685b',
+  brightRed: '#f07d6c',
+  brightGreen: '#7df79b',
+  brightYellow: '#ead17a',
+  brightBlue: '#76d0c8',
+  brightMagenta: '#92b8b2',
+  brightCyan: '#7ae7d6',
+  brightWhite: '#f3fff0'
 };
 
 // 默认 UI 主题 (CSS 变量)