chore: import upstream snapshot with attribution

tests/unit/compression/rtk-render-gitdiff.test.ts

@@ -0,0 +1,36 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { renderGitDiff } from "../../../open-sse/services/compression/engines/rtk/renderers/gitDiff.ts";
+
+const det = {
+  type: "git-diff",
+  command: "git diff",
+  confidence: 1,
+  category: "git",
+  matchedPatterns: [],
+};
+
+test("keeps file headers, hunks and +/- changes; drops context", () => {
+  const input = `diff --git a/x.ts b/x.ts
+index 111..222 100644
+--- a/x.ts
++++ b/x.ts
+@@ -1,3 +1,3 @@
+-const a = 1;
++const a = 2;
+ const b = 3;`;
+  const r = renderGitDiff(input, det);
+  assert.equal(r.changed, true);
+  assert.ok(r.text.includes("diff --git a/x.ts b/x.ts"));
+  assert.ok(r.text.includes("@@ -1,3 +1,3 @@"));
+  assert.ok(r.text.includes("-const a = 1;"));
+  assert.ok(r.text.includes("+const a = 2;"));
+  assert.ok(!r.text.includes("index 111..222"));
+  assert.ok(!r.text.includes("--- a/x.ts"));
+  assert.ok(!r.text.includes(" const b = 3;")); // contexto dropado
+});
+
+test("no hunks ⇒ no-op", () => {
+  const r = renderGitDiff("just some text\nno diff here", det);
+  assert.equal(r.changed, false);
+});