test(worktree): address embedded postgres helper review feedback

- probe host support on every platform instead of special-casing darwin
- re-export the db package helper from server and cli tests

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/db/src/test-embedded-postgres.ts

@@ -65,10 +65,6 @@ function formatEmbeddedPostgresError(error: unknown): string {
 }
 
 async function probeEmbeddedPostgresSupport(): Promise<EmbeddedPostgresTestSupport> {
-  if (process.platform !== "darwin") {
-    return { supported: true };
-  }
-
   const dataDir = fs.mkdtempSync(path.join(os.tmpdir(), "paperclip-embedded-postgres-probe-"));
   const port = await getAvailablePort();
   const EmbeddedPostgres = await getEmbeddedPostgresCtor();