v2.1.0

<!-- Release notes generated using configuration in .github/release.yml at main -->

## What's Changed
### 🚀 Features
* feat: Add Anthropic `_20260209` web tools with server-tool replay by @adtyavrdhn in https://github.com/pydantic/pydantic-ai/pull/4844
* Serialize instrumentation message attributes with to_json instead of json.dumps by @Kludex in https://github.com/pydantic/pydantic-ai/pull/6045
* Add TypeAdapter for EvaluatorContext by @hon-gyu in https://github.com/pydantic/pydantic-ai/pull/3373

### 🐛 Bug Fixes
* Convert `ExceptionGroup`-wrapped tool errors to `ModelRetry` in `MCPToolset` by @dmontagu in https://github.com/pydantic/pydantic-ai/pull/6004
* fix: prevent `cancel()` from flipping complete state on finished stream by @Oxygen56 in https://github.com/pydantic/pydantic-ai/pull/5795
* fix(temporal): add return type annotation to `PydanticAIPlugin.__init__` by @syf2211 in https://github.com/pydantic/pydantic-ai/pull/6065
* fix(anthropic): support Bedrock token counting by @dyscott in https://github.com/pydantic/pydantic-ai/pull/5480

## New Contributors
* @lucaszhu-hue made their first contribution in https://github.com/pydantic/pydantic-ai/pull/5982
* @syf2211 made their first contribution in https://github.com/pydantic/pydantic-ai/pull/6065
* @dyscott made their first contribution in https://github.com/pydantic/pydantic-ai/pull/5480
* @hon-gyu made their first contribution in https://github.com/pydantic/pydantic-ai/pull/3373

**Full Changelog**: https://github.com/pydantic/pydantic-ai/compare/v2.0.0...v2.1.0