test: migrate tests from centralized mjs to colocated TypeScript

Move test files from tests/ directory to colocate with source code,
convert from .mjs to .ts using tsx runner, add workspaces and npm
cache to CI workflow.

scripts/lib/shared-skill-packages.test.ts

@@ -0,0 +1,70 @@
+import assert from "node:assert/strict";
+import fs from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import test from "node:test";
+
+import { syncSharedSkillPackages } from "./shared-skill-packages.mjs";
+
+async function makeTempDir(prefix: string): Promise<string> {
+  return fs.mkdtemp(path.join(os.tmpdir(), prefix));
+}
+
+async function writeFile(filePath: string, contents = ""): Promise<void> {
+  await fs.mkdir(path.dirname(filePath), { recursive: true });
+  await fs.writeFile(filePath, contents);
+}
+
+async function writeJson(filePath: string, value: unknown): Promise<void> {
+  await writeFile(filePath, `${JSON.stringify(value, null, 2)}\n`);
+}
+
+test("syncSharedSkillPackages vendors workspace packages into skill scripts", async (t) => {
+  const root = await makeTempDir("baoyu-sync-shared-");
+  t.after(() => fs.rm(root, { recursive: true, force: true }));
+
+  await writeJson(path.join(root, "packages", "baoyu-md", "package.json"), {
+    name: "baoyu-md",
+    version: "1.0.0",
+  });
+  await writeFile(
+    path.join(root, "packages", "baoyu-md", "src", "index.ts"),
+    "export const markdown = true;\n",
+  );
+
+  const consumerDir = path.join(root, "skills", "demo-skill", "scripts");
+  await writeJson(path.join(consumerDir, "package.json"), {
+    name: "demo-skill-scripts",
+    version: "1.0.0",
+    dependencies: {
+      "baoyu-md": "^1.0.0",
+      kleur: "^4.1.5",
+    },
+  });
+
+  const result = await syncSharedSkillPackages(root, { install: false });
+
+  assert.deepEqual(result.packageDirs, [consumerDir]);
+  assert.deepEqual(result.managedPaths, [
+    "skills/demo-skill/scripts/bun.lock",
+    "skills/demo-skill/scripts/package.json",
+    "skills/demo-skill/scripts/vendor",
+  ]);
+
+  const updatedPackageJson = JSON.parse(
+    await fs.readFile(path.join(consumerDir, "package.json"), "utf8"),
+  ) as { dependencies: Record<string, string> };
+  assert.equal(updatedPackageJson.dependencies["baoyu-md"], "file:./vendor/baoyu-md");
+  assert.equal(updatedPackageJson.dependencies.kleur, "^4.1.5");
+
+  const vendoredPackageJson = JSON.parse(
+    await fs.readFile(path.join(consumerDir, "vendor", "baoyu-md", "package.json"), "utf8"),
+  ) as { name: string };
+  assert.equal(vendoredPackageJson.name, "baoyu-md");
+
+  const vendoredFile = await fs.readFile(
+    path.join(consumerDir, "vendor", "baoyu-md", "src", "index.ts"),
+    "utf8",
+  );
+  assert.match(vendoredFile, /markdown = true/);
+});