Inference APIs | Update Readme

[SSharma-10]

1. Add an AI & Inference section after the quickstart — chat streaming, image generation, and model listing examples. Currently invisible in the README.
2. Add a "New in v0.29.0" callout at the top linking down to the inference section. Developers need to know it exists before they scroll away.
3. Clarify api_key= vs token= The README only shows token= and the mismatch will silently break things for new users.
4. Update the Roadmap to mention inference. Right now it reads like an infrastructure-only SDK with no AI future.
5. Add examples/inference/ with three runnable scripts — one each for streaming chat, image gen, and model listing. The examples/ folder already exists, it just has nothing for inference.