test: add vitest unit tests across packages

Cover shared zod schemas, extract traversal/refs/downloads, and tts filename/error handling. Document the test setup in the README and docs.

packages/tts/src/index.test.ts

@@ -0,0 +1,56 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { getFileName } from './index.js';
+import { ItemNotFoundError, NoFileError, SteamApiError, TtsError } from './errors.js';
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+});
+
+describe('getFileName', () => {
+  it('parses a quoted content-disposition filename', () => {
+    expect(
+      getFileName('https://example.com/save', 'attachment; filename="mod.json"'),
+    ).toBe('mod.json');
+  });
+
+  it('parses an unquoted filename', () => {
+    expect(
+      getFileName('https://example.com/save', 'attachment; filename=mod.json'),
+    ).toBe('mod.json');
+  });
+
+  it('falls back to the URL path when there is no disposition', () => {
+    expect(getFileName('https://example.com/files/mod.json', null)).toBe(
+      'mod.json',
+    );
+  });
+
+  it('falls back to a default when the URL has no path', () => {
+    expect(getFileName('https://example.com', null)).toBe('save.json');
+  });
+});
+
+describe('error classes', () => {
+  it('ItemNotFoundError carries a 404 status', () => {
+    const err = new ItemNotFoundError('123');
+    expect(err).toBeInstanceOf(TtsError);
+    expect(err.status).toBe(404);
+    expect(err.message).toContain('123');
+  });
+
+  it('NoFileError carries a 404 status', () => {
+    const err = new NoFileError('123');
+    expect(err.status).toBe(404);
+    expect(err.message).toContain('123');
+  });
+
+  it('SteamApiError defaults to a 502 status', () => {
+    const err = new SteamApiError('boom');
+    expect(err.status).toBe(502);
+  });
+
+  it('TtsError defaults to a 500 status', () => {
+    const err = new TtsError('boom');
+    expect(err.status).toBe(500);
+  });
+});