Add initial VibeGuard browser extension

tests/hash.test.ts

@@ -0,0 +1,9 @@
+import { describe, expect, it } from "vitest";
+import { hashText, normalizeText } from "../src/shared/hash";
+
+describe("text hashing", () => {
+  it("normalizes whitespace and casing", () => {
+    expect(normalizeText("  Hello\n WORLD ")).toBe("hello world");
+    expect(hashText("hello  world")).toBe(hashText("HELLO\nWORLD"));
+  });
+});