接入原生壳文本文件导入能力

新增 file.importText HostBridge 契约和 H5 facade

移动端通过 Expo DocumentPicker 读取受控文本文件

桌面端通过 Tauri 文件选择框读取受控文本文件

更新壳能力检查、测试、方案文档和共享决策记录

apps/mobile-shell/src/mobileHostBridge.ts

@@ -1,4 +1,5 @@
 import * as Clipboard from 'expo-clipboard';
+import * as DocumentPicker from 'expo-document-picker';
 import { File, Paths } from 'expo-file-system';
 import * as Haptics from 'expo-haptics';
 import * as ImagePicker from 'expo-image-picker';
@@ -20,6 +21,7 @@ import {
   type FileExportTextPayload,
   type FileExportTextResult,
   type FileImportImageResult,
+  type FileImportTextResult,
   type HapticsImpactPayload,
   HOST_BRIDGE_PROTOCOL,
   HOST_BRIDGE_VERSION,
@@ -29,6 +31,7 @@ import {
   type HostBridgeMethod,
   type HostBridgeRequest,
   type HostBridgeResponse,
+  type HostBridgeTextMimeType,
   type NavigateNativePagePayload,
   normalizeHostBridgeBadgeCount,
   normalizeHostBridgeClipboardText,
@@ -46,8 +49,15 @@ import { getMobileNetworkStatus } from './mobileShellNetwork';
 const WEB_APP_ORIGIN = 'https://app.genarrative.world';
 const EXPORT_TEXT_MAX_BYTES = 5 * 1024 * 1024;
 const EXPORT_IMAGE_MAX_BYTES = 5 * 1024 * 1024;
+const IMPORT_TEXT_MAX_BYTES = 5 * 1024 * 1024;
 const IMPORT_IMAGE_MAX_BYTES = 10 * 1024 * 1024;
 const LOCAL_NOTIFICATION_CHANNEL_ID = 'genarrative-local';
+const HOST_BRIDGE_TEXT_MIME_TYPES = new Set<HostBridgeTextMimeType>([
+  'text/plain',
+  'text/markdown',
+  'text/csv',
+  'application/json',
+]);
 const HOST_BRIDGE_IMAGE_MIME_TYPES = new Set<HostBridgeImageMimeType>([
   'image/png',
   'image/jpeg',
@@ -78,6 +88,7 @@ export const MOBILE_HOST_CAPABILITIES: HostBridgeCapability[] = [
   'clipboard.writeText',
   'clipboard.readText',
   'file.exportText',
+  'file.importText',
   'file.exportImage',
   'file.importImage',
   'haptics.impact',
@@ -283,6 +294,82 @@ async function exportTextFile(payload: unknown): Promise<FileExportTextResult> {
   };
 }
 
+function normalizeImportedTextMimeType(
+  value: unknown,
+  fileName: string,
+): HostBridgeTextMimeType | null {
+  if (typeof value === 'string') {
+    const mimeType = value.toLowerCase();
+    if (HOST_BRIDGE_TEXT_MIME_TYPES.has(mimeType as HostBridgeTextMimeType)) {
+      return mimeType as HostBridgeTextMimeType;
+    }
+  }
+
+  const normalizedName = fileName.toLowerCase();
+  if (normalizedName.endsWith('.json')) {
+    return 'application/json';
+  }
+  if (normalizedName.endsWith('.md') || normalizedName.endsWith('.markdown')) {
+    return 'text/markdown';
+  }
+  if (normalizedName.endsWith('.csv')) {
+    return 'text/csv';
+  }
+  if (normalizedName.endsWith('.txt')) {
+    return 'text/plain';
+  }
+
+  return null;
+}
+
+async function importTextFile(): Promise<FileImportTextResult> {
+  const result = await DocumentPicker.getDocumentAsync({
+    copyToCacheDirectory: true,
+    multiple: false,
+    type: ['text/*', 'application/json'],
+  });
+  if (result.canceled) {
+    throw {
+      code: 'cancelled',
+      message: 'file import cancelled',
+    } satisfies HostBridgeError;
+  }
+
+  const asset = result.assets[0];
+  if (!asset?.uri) {
+    throw invalidRequest('text file is required');
+  }
+
+  const fileName = normalizeHostBridgeExportFileName(
+    asset.name || 'genarrative-import.txt',
+  );
+  const mimeType = normalizeImportedTextMimeType(asset.mimeType, fileName);
+  if (!mimeType) {
+    throw invalidRequest('mimeType must be an allowed text type');
+  }
+  if (
+    typeof asset.size === 'number' &&
+    (asset.size <= 0 || asset.size > IMPORT_TEXT_MAX_BYTES)
+  ) {
+    throw invalidRequest('text exceeds file import size limit');
+  }
+
+  const file = new File(asset.uri);
+  const content = await file.text();
+  const bytes = utf8ByteLength(content);
+  if (bytes <= 0 || bytes > IMPORT_TEXT_MAX_BYTES) {
+    throw invalidRequest('text exceeds file import size limit');
+  }
+
+  return {
+    action: 'selected',
+    fileName,
+    content,
+    mimeType,
+    bytes,
+  };
+}
+
 async function exportImageFile(payload: unknown): Promise<FileExportImageResult> {
   const exportPayload = payload as FileExportImagePayload | undefined;
   const mimeType = exportPayload?.mimeType;
@@ -627,6 +714,8 @@ async function handleRequest(request: HostBridgeRequest) {
       return ok(request, await readClipboard());
     case 'file.exportText':
       return ok(request, await exportTextFile(request.payload));
+    case 'file.importText':
+      return ok(request, await importTextFile());
     case 'file.exportImage':
       return ok(request, await exportImageFile(request.payload));
     case 'file.importImage':