fix(xwebview): 将 react-native-blob-util 改为懒加载以兼容 RN 0.85 Bridgeless 模式

静态 import 会在模块评估时触发 fs.js:14 调用 ReactNativeBlobUtil.getConstants()，
在 Bridgeless 模式下 TurboModule 未注册时返回 null 导致崩溃。
改为在函数体内 require() 延迟至实际下载时才初始化。

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/xwebview/src/XWebViewDownload.ts

@@ -1,5 +1,4 @@
 import { Platform } from 'react-native'
-import RNFetchBlob from 'react-native-blob-util'
 
 import type {
   XWebViewDownloadDecision,
@@ -8,6 +7,11 @@ import type {
   XWebViewDownloadResult,
 } from '@xuqm/rn-common'
 
+// Lazy import: react-native-blob-util calls getConstants() at module evaluation time,
+// which crashes in RN 0.85 Bridgeless mode. Defer the require until actual download use.
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+const getRNFetchBlob = () => (require('react-native-blob-util') as { default: typeof import('react-native-blob-util').default }).default
+
 function parseContentDispositionFilename(header: string): string | null {
   const rfc5987 = header.match(/filename\*=(?:[^']*'[^']*')?([^;\s]+)/i)
   if (rfc5987?.[1]) {
@@ -70,7 +74,7 @@ async function resolveFilePath(
   const full = `${dir}/${filename}`
   if (conflict === 'overwrite') return full
 
-  const exists = await RNFetchBlob.fs.exists(full)
+  const exists = await getRNFetchBlob().fs.exists(full)
   if (!exists) return full
 
   const dot = filename.lastIndexOf('.')
@@ -82,7 +86,7 @@ async function resolveFilePath(
   do {
     candidate = `${dir}/${base}(${n})${ext}`
     n++
-  } while (await RNFetchBlob.fs.exists(candidate))
+  } while (await getRNFetchBlob().fs.exists(candidate))
 
   return candidate
 }
@@ -93,14 +97,14 @@ export async function saveBase64File(
   savePath: string | undefined,
   conflict: 'rename' | 'overwrite',
 ): Promise<string> {
-  const { dirs } = RNFetchBlob.fs
+  const { dirs } = getRNFetchBlob().fs
   const dir =
     savePath ??
     (Platform.OS === 'android'
       ? (dirs.DownloadDir ?? dirs.DocumentDir)
       : dirs.DocumentDir)
   const filePath = await resolveFilePath(dir, filename, conflict)
-  await RNFetchBlob.fs.writeFile(filePath, base64, 'base64')
+  await getRNFetchBlob().fs.writeFile(filePath, base64, 'base64')
   return filePath
 }
 
@@ -176,7 +180,7 @@ export function startDownload(
   onComplete: (r: XWebViewDownloadResult) => void,
   onError: (error: string) => void,
 ): DownloadHandle {
-  const { dirs } = RNFetchBlob.fs
+  const { dirs } = getRNFetchBlob().fs
   const dir =
     savePath ??
     (Platform.OS === 'android'
@@ -192,7 +196,7 @@ export function startDownload(
     .then(filePath => {
       if (cancelled) return
 
-      const task = RNFetchBlob.config({ path: filePath }).fetch('GET', url)
+      const task = getRNFetchBlob().config({ path: filePath }).fetch('GET', url)
       cancelFn = () => task.cancel()
 
       task.progress({ interval: 300 }, (received: number, total: number) => {