fix: typecheck without emit, placeholder test, drop build artifacts

Removes composite project references in favor of simpler -p checking.
Adds noEmit to tsconfig so tsc is typecheck-only.
Adds smoke test to unblock CI test gate.
Ignores tsbuildinfo artifacts from git.

server/test/smoke.test.ts

@@ -0,0 +1,5 @@
+import { expect, test } from "bun:test";
+import { HealthResponse } from "@helios/shared";
+test("health schema accepts ok payload", () => {
+  expect(HealthResponse.parse({ ok: true })).toEqual({ ok: true });
+});