Structured adherence and streaming

• Built out the whole structured-generation stack: JsonAdherence with retries, schema + semantic validators, pluggable grammar wrappers, and a GenerateResult object that carries attempts/violations.
• Added a streaming engine with incremental JSON validation, token callbacks, and stop_on_invalid control; MLX backend now streams tokens while enforcing schemas in real time.
• Exposed high-level helpers (StructuredSpec, generate_structured, generate_many, semantic predicates) plus logging/eval utilities and a JSONL adherence logger.
• Expanded docs and examples (README + examples/structured_generation.py) so users can see structured and streaming workflows end to end, including the new CLI flags.
• Broadened tests: unit coverage for the adherence/streaming engines, a stubbed eval-suite smoke test, and integration demos.
• Polished packaging/release workflow with make publish, release notes, and metadata fixes so PyPI uploads succeed cleanly.