接入原生壳外观查询能力

新增 HostBridge appearance.getColorScheme 只读契约和 H5 facade

Expo 壳通过 React Native Appearance 读取系统配色

Tauri 壳通过主窗口 theme 读取桌面配色

补齐外观查询测试、漂移检查和架构文档

src/services/host-bridge/hostBridge.ts

@@ -1,4 +1,5 @@
 import type {
+  AppearanceColorSchemeResult,
   FileExportImagePayload,
   FileExportImageResult,
   FileExportTextPayload,
@@ -14,6 +15,7 @@ import type {
 import {
   isHostBridgeCapability,
   normalizeHostBridgeBadgeCount,
+  normalizeHostBridgeColorScheme,
   normalizeHostBridgeExternalUrl,
 } from '../../../packages/shared/src/contracts/hostBridge';
 import type {
@@ -95,6 +97,8 @@ export type HostShareOpenRequest = ShareOpenPayload;
 
 export type HostExternalUrlRequest = OpenExternalUrlPayload;
 
+export type HostAppearanceColorSchemeSnapshot = AppearanceColorSchemeResult;
+
 const HOST_RUNTIME_REFRESH_TIMEOUT_MS = 3000;
 
 let cachedNativeHostRuntime: HostBridgeRuntimeResult | null = null;
@@ -764,3 +768,21 @@ export async function setHostAppBadgeCount({
     return false;
   }
 }
+
+export async function getHostAppearanceColorScheme() {
+  if (!canUseNativeHostCapability('appearance.getColorScheme')) {
+    return false;
+  }
+
+  try {
+    const result =
+      await requestNativeAppHostBridge<AppearanceColorSchemeResult>(
+        'appearance.getColorScheme',
+      );
+    return {
+      colorScheme: normalizeHostBridgeColorScheme(result?.colorScheme),
+    } satisfies HostAppearanceColorSchemeSnapshot;
+  } catch {
+    return false;
+  }
+}