feat: Unify spark table detection and content resolution

Export isSparkTableHeader from content-registry and use it in both CLI
and frontend table parsing. Add resolveContentRef to resolve content
references consistently. Write processed registry content back to the
file index so browser mode renders identically to CLI mode.

src/data-loader/file-index.ts

@@ -17,6 +17,7 @@ import {
   removeHandle,
   ensurePermission,
 } from "./file-index-db";
+import { normalizePathKey } from "../cli/content-registry";
 
 type FileIndex = Record<string, string>;
 
@@ -99,7 +100,7 @@ async function scanDirectory(
       Object.assign(index, sub);
     } else if (entry.kind === "file" && acceptedExt.test(name)) {
       const file = await (entry as FileSystemFileHandle).getFile();
-      const path = prefix + name;
+      const path = normalizePathKey(prefix + name);
       index[path] = await file.text();
     }
   }
@@ -211,6 +212,16 @@ export async function getIndexedData(path: string): Promise<string> {
   return content;
 }
 
+/**
+ * 写入/覆盖索引中的文件内容。
+ * 用于将处理后的内容（如 registry 的 stripped markdown）写回索引，
+ * 使浏览器模式与 CLI 模式渲染一致。
+ */
+export function setIndexedData(path: string, content: string): void {
+  fileIndex = fileIndex || {};
+  fileIndex[normalizePathKey(path)] = content;
+}
+
 /**
  * 获取指定扩展名的文件路径
  */