fix(skill): patch up skill diffing code (#758)

Co-authored-by: Letta <noreply@letta.com>

src/tests/skills/syncing-memory-filesystem-scripts.test.ts

@@ -0,0 +1,47 @@
+/**
+ * Tests for syncing-memory-filesystem script helpers
+ */
+
+import { describe, expect, test } from "bun:test";
+import { createHash } from "node:crypto";
+import { parseMdxFrontmatter } from "../../agent/memory";
+import {
+  hashFileBody,
+  parseFrontmatter,
+} from "../../skills/builtin/syncing-memory-filesystem/scripts/lib/frontmatter";
+
+describe("syncing-memory-filesystem script frontmatter helpers", () => {
+  test("parseFrontmatter matches parseMdxFrontmatter and trims body", () => {
+    const content = [
+      "---",
+      "description: Test description",
+      "limit: 123",
+      "---",
+      "",
+      "Hello world",
+      "",
+    ].join("\n");
+
+    const parsed = parseFrontmatter(content);
+    const expected = parseMdxFrontmatter(content);
+
+    expect(parsed).toEqual(expected);
+    expect(parsed.body).toBe("Hello world");
+  });
+
+  test("hashFileBody uses trimmed body (no leading newline)", () => {
+    const content = [
+      "---",
+      "description: Test description",
+      "---",
+      "",
+      "Line one",
+      "Line two",
+    ].join("\n");
+
+    const { body } = parseMdxFrontmatter(content);
+    const expectedHash = createHash("sha256").update(body).digest("hex");
+
+    expect(hashFileBody(content)).toBe(expectedHash);
+  });
+});