Update examples to support UDS-only builds (no embedded tokenizers)

[sagearc]

Description

As part of the effort to isolate and deprecate embedded tokenizers (#295), all example binaries are now gated behind the embedded_tokenizers build tag (#303). This means every example requires Python/CGO to build, and there is no reference example demonstrating the recommended UDS tokenizer architecture.

Parent issue: #295
Build tag isolation PR: #303
Related: #298 (E2E tests for UDS tokenizer)