refactor(mcp-server): make the diagram modules usable from the web app

The web app will reuse the MCP server's XML engine instead of its own
copy in lib/utils.ts, so these modules now run in the browser too.

- Relative imports end in .ts, rewritten to .js by tsc
  (rewriteRelativeImportExtensions); Next.js resolves them directly
- Every module uses the global DOMParser/XMLSerializer: native in the
  browser, linkedom in Node via installDomPolyfill. pages.ts parsed with
  linkedom but serialized with the global serializer, which throws in
  the browser
- The saxes syntax check moves to xml-syntax.ts, so the browser does not
  pull in linkedom; it now also rejects undeclared prefixes such as
  xlink:, as the browser does
- Page decompression uses pako and atob instead of node:zlib and Buffer
- hasCells moves to pages.ts, away from the file system code
- The duplicate cell id check counts UserObject/object ids
- wrapCellsInModel drops comments and text before the first cell, which
  the web app accepts today
- validateAndFixXml takes { strict: false } for diagrams with user content
- Web tests run these modules with a browser DOM (jsdom)
- saxes becomes a direct dependency of the web app

packages/mcp-server/src/index.ts

@@ -24,12 +24,12 @@ import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js"
 import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js"
 import open from "open"
 import { z } from "zod"
-import type { DiagramOperation } from "./diagram-operations.js"
-import { installDomPolyfill } from "./dom.js"
-import { DRAWING_GUIDE } from "./drawing-guide.js"
-import { editDiagram, targetPageXml } from "./edit-diagram.js"
-import { checkEditGate } from "./edit-gate.js"
-import { addHistory } from "./history.js"
+import type { DiagramOperation } from "./diagram-operations.ts"
+import { installDomPolyfill } from "./dom.ts"
+import { DRAWING_GUIDE } from "./drawing-guide.ts"
+import { editDiagram, targetPageXml } from "./edit-diagram.ts"
+import { checkEditGate } from "./edit-gate.ts"
+import { addHistory } from "./history.ts"
 import {
     type ExportFormat,
     type ExportOptions,
@@ -42,13 +42,14 @@ import {
     shutdown,
     startHttpServer,
     waitForSync,
-} from "./http-server.js"
-import { parseDrawioFileContent } from "./load-diagram.js"
-import { log } from "./logger.js"
+} from "./http-server.ts"
+import { parseDrawioFileContent } from "./load-diagram.ts"
+import { log } from "./logger.ts"
 import {
     addPageToDoc,
     deletePageFromDoc,
     findPageElement,
+    hasCells,
     hasPageSelector,
     listPagesFromDoc,
     normalizeToMxfile,
@@ -58,10 +59,10 @@ import {
     renamePageInDoc,
     serializeMxfile,
     wrapCellsInModel,
-} from "./pages.js"
-import { Autosaver, defaultDataDir, hasCells } from "./persistence.js"
-import { getShapeLibrary, SHAPE_LIBRARY_GROUPS } from "./shape-library.js"
-import { validateAndFixXml } from "./xml-validation.js"
+} from "./pages.ts"
+import { Autosaver, defaultDataDir } from "./persistence.ts"
+import { getShapeLibrary, SHAPE_LIBRARY_GROUPS } from "./shape-library.ts"
+import { validateAndFixXml } from "./xml-validation.ts"
 
 // DOMParser/XMLSerializer globals for the XML helpers (Node has neither)
 installDomPolyfill()