Summary:
- set the package version to 0.2.0
- add the 0.2.0 changelog entry
- update the README install snippet and remove direct example links

Rationale:
- align the public release surface with the current API and docs
- prepare the repo for the local release steps in RELEASE.md

Validation:
- mix test
- mix docs
- mix hex.build

Co-authored-by: Codex <codex@openai.com>