Revert "Revert "feat: 第一个可以用的 ink 组件抽象 (#158)" (#175)"

This reverts commit 88d4c3ba24.

packages/@ant/ink/src/theme/systemTheme.ts

@@ -0,0 +1,40 @@
+/**
+ * Terminal dark/light mode detection.
+ *
+ * Detection is based on the terminal's actual background color (queried via
+ * OSC 11) rather than the OS appearance setting.
+ *
+ * Vendored from src/utils/systemTheme.ts for package independence.
+ */
+
+export type SystemTheme = 'dark' | 'light'
+
+let cachedSystemTheme: SystemTheme | undefined
+
+/**
+ * Detect theme from $COLORFGBG environment variable (set by some terminals).
+ */
+function detectFromColorFgBg(): SystemTheme | undefined {
+  const colorFgBg = process.env.COLORFGBG
+  if (!colorFgBg) return undefined
+  const parts = colorFgBg.split(';')
+  if (parts.length < 2) return undefined
+  const bg = parseInt(parts[parts.length - 1]!, 10)
+  // Standard ANSI color indices: 0-7 are dark, 8-15 are bright/light
+  if (isNaN(bg)) return undefined
+  return bg >= 8 ? 'light' : 'dark'
+}
+
+/**
+ * Get the current terminal theme. Cached after first detection.
+ */
+export function getSystemThemeName(): SystemTheme {
+  if (cachedSystemTheme === undefined) {
+    cachedSystemTheme = detectFromColorFgBg() ?? 'dark'
+  }
+  return cachedSystemTheme
+}
+
+export function setCachedSystemTheme(theme: SystemTheme): void {
+  cachedSystemTheme = theme
+}