fix: fix plan mode path resolution on Windows (#365)

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

src/tests/helpers/planName.test.ts

@@ -0,0 +1,28 @@
+import { expect, test } from "bun:test";
+import { sep } from "node:path";
+import {
+  generatePlanFilePath,
+  generatePlanName,
+} from "../../cli/helpers/planName";
+
+test("generatePlanName returns valid format", () => {
+  const name = generatePlanName();
+  expect(name).toMatch(/^[a-z]+-[a-z]+-[a-z]+$/);
+});
+
+test("generatePlanFilePath uses platform-specific path separator", () => {
+  const path = generatePlanFilePath();
+  expect(path).toContain(sep);
+  expect(path).toMatch(/\.letta.+plans.+/);
+});
+
+test("generatePlanFilePath ends with .md extension", () => {
+  const path = generatePlanFilePath();
+  expect(path).toMatch(/\.md$/);
+});
+
+test("generatePlanFilePath contains valid plan name structure", () => {
+  const path = generatePlanFilePath();
+  const basename = path.split(sep).pop();
+  expect(basename).toMatch(/^[a-z]+-[a-z]+-[a-z]+\.md$/);
+});