feat: integrate Anthropic batching support across docs and tooling

[AnsonDev42]

Summary

• Added Anthropic batching provider support and wired it into the provider registry, CLI, and core models.
• Expanded live and unit coverage for Anthropic flows, CLI behavior, architecture, and agent tooling.
• Updated the docs, getting-started guides, API reference, roadmap, and smoke-test guidance to reflect the new provider and workflows.

Testing

• Added and updated unit tests for Anthropic provider behavior, CLI integration, architecture expectations, and agent tooling.
• Added a live integration test for Anthropic batching.
• Updated smoke-test documentation; repo validation was not run as part of this change.