fix(messages): normalize escaped markdown newlines

tests/unit/markdown-text.test.ts

@@ -0,0 +1,12 @@
+import { describe, expect, it } from "vitest";
+import { normalizeMarkdownText } from "../../src/shared/markdown-text";
+
+describe("normalizeMarkdownText", () => {
+  it("converts escaped markdown line breaks into renderable markdown", () => {
+    expect(normalizeMarkdownText("Intro\\n\\n## Plan\\n- First\\n- Second")).toBe("Intro\n\n## Plan\n- First\n- Second");
+  });
+
+  it("normalizes actual CRLF input to LF", () => {
+    expect(normalizeMarkdownText("One\r\nTwo\rThree")).toBe("One\nTwo\nThree");
+  });
+});