feat: switch logging to pino

Closes HP-279

tests/unit/utils/log.test.ts

@@ -0,0 +1,59 @@
+import { beforeEach, describe, expect, test, vi } from "vitest";
+
+const envSnapshot = { ...process.env };
+
+async function loadLogger() {
+  vi.resetModules();
+  const mod = await import("~/utils/log");
+  return mod.default;
+}
+
+describe("structured logger", () => {
+  beforeEach(() => {
+    process.env = { ...envSnapshot };
+    vi.restoreAllMocks();
+  });
+
+  test("writes JSON log entries", async () => {
+    process.env.HEADPLANE_DEBUG_LOG = "false";
+    const spy = vi.spyOn(process.stdout, "write").mockImplementation(() => true);
+    const log = await loadLogger();
+
+    log.info("server", "Listening on %s://%s:%s", "http", "127.0.0.1", 3000);
+
+    expect(spy).toHaveBeenCalledOnce();
+    const entry = JSON.parse(spy.mock.calls[0][0] as string);
+    expect(entry).toMatchObject({
+      level: "info",
+      component: "server",
+      msg: "Listening on http://127.0.0.1:3000",
+    });
+    expect(entry.timestamp).toEqual(expect.any(String));
+  });
+
+  test("keeps debug logs disabled by default", async () => {
+    delete process.env.HEADPLANE_DEBUG_LOG;
+    const spy = vi.spyOn(process.stdout, "write").mockImplementation(() => true);
+    const log = await loadLogger();
+
+    log.debug("api", "GET %s", "/v1/node");
+
+    expect(log.debugEnabled).toBe(false);
+    expect(spy).not.toHaveBeenCalled();
+  });
+
+  test("writes debug entries when enabled", async () => {
+    process.env.HEADPLANE_DEBUG_LOG = "true";
+    const spy = vi.spyOn(process.stdout, "write").mockImplementation(() => true);
+    const log = await loadLogger();
+
+    log.debug("api", "GET %s", "/v1/node");
+
+    expect(log.debugEnabled).toBe(true);
+    expect(JSON.parse(spy.mock.calls[0][0] as string)).toMatchObject({
+      level: "debug",
+      component: "api",
+      msg: "GET /v1/node",
+    });
+  });
+});