Feature Request: Add clear lifecycle and support expectations to README

### Is your feature request related to a problem? Please describe.

The `base/account-sdk` README focuses primarily on usage examples and API surface, but it does not clearly communicate lifecycle, support expectations, or intended usage boundaries (e.g., experimental vs stable APIs).

### Describe the solution you'd like

- Add a dedicated section to the README (e.g. “Project Status” or “Stability & Support”).
- Clearly document:
- current maturity level (stable, evolving, experimental)
- expectations around breaking changes and versioning
- intended usage (production-ready vs early adoption)
- Optionally reference related resources such as release notes or changelog.

### Acceptance Criteria
- README includes a clear and concise section describing project status and expectations.
- Developers can easily assess whether the SDK fits their production needs.
- No changes are made to SDK behavior or public APIs.
- Documentation remains easy to maintain and update over time.

### Additional context

_No response_

Start with the README and inspect any available release notes or changelog for project-status information. Add a concise, maintainable section covering maturity, breaking-change and versioning expectations, and intended production use; done means the acceptance criteria are met without changing SDK behavior or public APIs.

Written by the indexing model from the issue text.