refactor(lib): reuse MCP helpers for streaming preview and SVG extraction

- lib/utils.ts: remove convertToLegalXml and replaceNodes; the streaming
  preview now goes through wrapCellsInModel, autoFixXml and
  replacePageModel like the final commit path does
- lib/utils.ts: extractDiagramXML reuses extractSvgEmbeddedXml,
  pageElement and decompressPageContent instead of hand-written SVG
  parsing and pako inflation
- lib/use-file-processor.tsx: messages parameter is required, drop the
  English default texts only tests used
- hooks/use-dictionary.ts, lib/i18n/utils.ts: drop duplicate default
  exports nobody imported
- tests updated accordingly

tests/unit/use-diagram-streaming.test.tsx

@@ -103,6 +103,35 @@ describe("the streaming preview of display_diagram", () => {
         expect(loaded).not.toContain("mxStyle")
         expect(loaded).not.toContain('id="b"')
     })
+
+    it("fixes an unescaped & and HTML in a label, as the final diagram does", () => {
+        mocks.loadDiagram.mockClear()
+        const xml = `<mxCell id="a" value="R & D <b>team</b>" vertex="1" parent="1"><mxGeometry x="0" y="0" width="80" height="40" as="geometry"/></mxCell>`
+        renderHook(() =>
+            useDiagramStreaming({
+                messages: [
+                    {
+                        id: "m1",
+                        role: "assistant",
+                        parts: [
+                            {
+                                type: "tool-display_diagram",
+                                toolCallId: "draw-2",
+                                state: "input-streaming",
+                                input: { xml },
+                            },
+                        ],
+                    },
+                ] as any,
+                processedToolCallsRef: { current: new Set() },
+                editDiagramOriginalXmlRef: { current: new Map() },
+                loadedMessageIdsRef: { current: new Set() },
+            }),
+        )
+        expect(mocks.loadDiagram).toHaveBeenCalledTimes(1)
+        const loaded = mocks.loadDiagram.mock.calls[0][0]
+        expect(loaded).toContain('value="R &amp; D &lt;b&gt;team&lt;/b&gt;"')
+    })
 })
 
 describe("the streaming preview of edit_diagram", () => {

tests/unit/use-file-processor.test.tsx

@@ -22,6 +22,8 @@ function deferred<T>() {
 const pdfFile = () =>
     new File(["%PDF"], "slow.pdf", { type: "application/pdf" })
 const textFile = () => new File(["notes"], "notes.txt", { type: "text/plain" })
+// The toast texts the hook formats; toast is mocked, so any texts do
+const messages = { tooLong: "{name} too long", readFailed: "failed {name}" }
 
 describe("useFileProcessor", () => {
     beforeEach(() => {
@@ -35,7 +37,7 @@ describe("useFileProcessor", () => {
         vi.mocked(extractTextFileContent).mockResolvedValue("notes")
         const a = pdfFile()
         const b = textFile()
-        const { result } = renderHook(() => useFileProcessor())
+        const { result } = renderHook(() => useFileProcessor(messages))
 
         let done!: Promise<void>
         act(() => {
@@ -59,7 +61,7 @@ describe("useFileProcessor", () => {
         vi.mocked(extractTextFileContent).mockResolvedValue("notes")
         const a = pdfFile()
         const b = textFile()
-        const { result } = renderHook(() => useFileProcessor())
+        const { result } = renderHook(() => useFileProcessor(messages))
 
         let first!: Promise<void>
         act(() => {
@@ -82,7 +84,7 @@ describe("useFileProcessor", () => {
         const pdf = deferred<string>()
         vi.mocked(extractPdfText).mockReturnValue(pdf.promise)
         const a = pdfFile()
-        const { result } = renderHook(() => useFileProcessor())
+        const { result } = renderHook(() => useFileProcessor(messages))
 
         let first!: Promise<void>
         act(() => {

tests/unit/utils.test.ts

@@ -5,7 +5,6 @@ import {
     extractCompleteMxCells,
     extractDiagramXML,
     isRealDiagram,
-    replaceNodes,
 } from "@/lib/utils"
 import { BLANK_MXFILE } from "@/packages/mcp-server/src/pages.ts"
 
@@ -70,39 +69,6 @@ describe("extractCompleteMxCells", () => {
 const pageBox = (id: string) => `<mxCell id="${id}" vertex="1" parent="1"/>`
 const pageModel = (cells: string) =>
     `<mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/>${cells}</root></mxGraphModel>`
-const pageOf = (id: string, cells: string) =>
-    `<diagram id="${id}" name="${id}">${pageModel(cells)}</diagram>`
-/** Ids of the shapes on a page (not the root cells) */
-const shapesOn = (xml: string, pageId: string) =>
-    Array.from(
-        new DOMParser()
-            .parseFromString(xml, "text/xml")
-            .querySelectorAll(`diagram[id="${pageId}"] mxCell`),
-    )
-        .map((cell) => cell.getAttribute("id"))
-        .filter((id) => id !== "0" && id !== "1")
-
-describe("replaceNodes", () => {
-    const two = `<mxfile>${pageOf("a", pageBox("A"))}${pageOf("b", pageBox("B"))}</mxfile>`
-
-    it("replaces the first page's cells by default", () => {
-        const out = replaceNodes(two, pageBox("N"))
-        expect(shapesOn(out, "a")).toEqual(["N"])
-        expect(shapesOn(out, "b")).toEqual(["B"])
-    })
-
-    it("replaces the given page's cells and keeps the others", () => {
-        const out = replaceNodes(two, pageBox("N"), "b")
-        expect(shapesOn(out, "a")).toEqual(["A"])
-        expect(shapesOn(out, "b")).toEqual(["N"])
-    })
-
-    it("uses the first page when the given page is not there", () => {
-        const out = replaceNodes(two, pageBox("N"), "zzz")
-        expect(shapesOn(out, "a")).toEqual(["N"])
-        expect(shapesOn(out, "b")).toEqual(["B"])
-    })
-})
 
 describe("extractDiagramXML", () => {
     const packed = (model: string) =>