feat: introduce local-first SVG workbench

tests/format/format-and-diff.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from "vitest";
+import { lineDiff } from "../../src/format/diff";
+import { formatSvgSource } from "../../src/format/formatter";
+
+describe("explicit formatting and source diff", () => {
+  it("formats only when explicitly requested and retains CRLF style", () => {
+    const source =
+      '<svg xmlns="http://www.w3.org/2000/svg" z="2" a="1">\r\n<g><title>A &amp; B</title></g>\r\n</svg>';
+    const formatted = formatSvgSource(source);
+    expect(formatted).toContain("\r\n  <g>\r\n    <title>A &amp; B</title>");
+    expect(formatted).toContain(' a="1" z="2"');
+    expect(formatted.endsWith("\r\n")).toBe(true);
+  });
+
+  it("refuses to format malformed XML", () => {
+    expect(() => formatSvgSource("<svg><g")).toThrow(/well-formed/u);
+  });
+
+  it("produces stable line additions, removals and context", () => {
+    expect(lineDiff("a\nb\nc", "a\nx\nc")).toEqual([
+      { kind: "same", text: "a", oldLine: 1, newLine: 1 },
+      { kind: "add", text: "x", newLine: 2 },
+      { kind: "remove", text: "b", oldLine: 2 },
+      { kind: "same", text: "c", oldLine: 3, newLine: 3 },
+    ]);
+  });
+
+  it("falls back to bounded summaries for large comparisons", () => {
+    expect(lineDiff("a\nb\nc", "d\ne\nf", 2)).toEqual([
+      { kind: "remove", text: "3 lines (5 characters)", oldLine: 1 },
+      { kind: "add", text: "3 lines (5 characters)", newLine: 1 },
+    ]);
+  });
+});