chore: import upstream snapshot with attribution

tests/unit/ui/compressionAnnotation.test.tsx

@@ -0,0 +1,67 @@
+// @vitest-environment jsdom
+import React from "react";
+import { act } from "react";
+import { createRoot } from "react-dom/client";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { CompressionAnnotation } from "@/app/(dashboard)/dashboard/compression/studio/CompressionAnnotation";
+import type { CompressionStats } from "@omniroute/open-sse/services/compression/types";
+
+let container: HTMLDivElement;
+
+beforeEach(() => {
+  container = document.createElement("div");
+  document.body.appendChild(container);
+});
+
+afterEach(() => {
+  document.body.removeChild(container);
+});
+
+function render(ui: React.ReactElement) {
+  act(() => {
+    createRoot(container).render(ui);
+  });
+}
+
+function makeStats(overrides: Partial<CompressionStats> = {}): CompressionStats {
+  return {
+    originalTokens: 847,
+    compressedTokens: 312,
+    savingsPercent: 63.16,
+    techniquesUsed: ["caveman"],
+    mode: "standard",
+    timestamp: 0,
+    ...overrides,
+  };
+}
+
+describe("CompressionAnnotation", () => {
+  it("renders token range badge", () => {
+    const stats = makeStats({
+      rulesApplied: ["filler", "filler", "dedup"],
+    });
+    render(<CompressionAnnotation stats={stats} />);
+    expect(container.textContent).toContain("847→312");
+  });
+
+  it("renders rule pills", () => {
+    const stats = makeStats({
+      rulesApplied: ["filler", "filler", "dedup"],
+    });
+    render(<CompressionAnnotation stats={stats} />);
+    expect(container.textContent).toContain("filler×2");
+    expect(container.textContent).toContain("dedup×1");
+  });
+
+  it("returns null when no rules applied", () => {
+    const stats = makeStats({ rulesApplied: [], techniquesUsed: [] });
+    render(<CompressionAnnotation stats={stats} />);
+    expect(container.innerHTML).toBe("");
+  });
+
+  it("returns null when rulesApplied is absent", () => {
+    const stats = makeStats({ rulesApplied: undefined, techniquesUsed: [] });
+    render(<CompressionAnnotation stats={stats} />);
+    expect(container.innerHTML).toBe("");
+  });
+});