v2.22.0

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

## What's Changed
### 🚀 Features
* Allow `MCPToolset` clients to skip optional MCP tasks via `prefer_tasks` by @adtyavrdhn in https://github.com/pydantic/pydantic-ai/pull/6851
* Default Gemini `VALIDATED` tool mode on supported models by @hramezani in https://github.com/pydantic/pydantic-ai/pull/6353
* Stop advertising tool search for capability-owned deferred tools on Anthropic by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6770
* Send mid-conversation system prompts as native `system` messages on Anthropic by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6765
* Add `RunContext.is_tool_available` by @DouweM in https://github.com/pydantic/pydantic-ai/pull/7011
### 🐛 Bug Fixes
* Handle closed event loops in synchronous APIs by @adtyavrdhn in https://github.com/pydantic/pydantic-ai/pull/6850
* Compare full origin, not just hostname, when dropping credentials on `safe_download` redirects by @pydanty[bot] in https://github.com/pydantic/pydantic-ai/pull/6811
* Fix Temporal workflow livelock when anyio scope cancellation hits an in-flight activity await by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6892
* Copy `extra_headers` before `setdefault` in OpenAI chat and Groq models by @pydanty[bot] in https://github.com/pydantic/pydantic-ai/pull/6868
* Support requesting approval or deferring a call from a tool's `args_validator` by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6897
* Use the workflow-prepared `tool_def` in Temporal function-tool activities instead of re-running `prepare` by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6890
* Raise a `UserError` instead of hanging when `run_sync()` is called on an event loop it cannot drive by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6905
* Fix Prefect tool-call cache keys: replay tool results on flow retry and stop colliding on `RunContext` fields a tool can read by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6944
* Run `after_tool_validate` when an `args_validator` defers the call by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6961
* Preserve the host's Logfire configuration in the Temporal `LogfirePlugin` by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6962
* Fail the workflow instead of retrying forever when a Temporal activity argument can't be serialized by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6893
* Install the `EnqueueGuard` on the DBOS/Prefect model-request and `cancel_suspended_response` units by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6943
* Restore typed values in a dynamic tool's Temporal `ActivityConfig` after the activity round trip by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6947
* Reject unregistered `Model` instances in durable runs instead of re-inferring them from `model_id` by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6898
* Heartbeat in tool, MCP, dynamic-toolset, and event-stream Temporal activities by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6965
* Rehydrate `set`s, carry `conversation_id`, and hard-error on omitted fields in `TemporalRunContext` by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6891
* Allow `ApprovalRequired`/`CallDeferred` from post-validation tool hooks, `UserError` from pre-validation ones by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6951
* Raise a `UserError` when a history processor or `fallback_on` handler has unresolvable type annotations by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6958
* Raise `ModelAPIError` for OpenRouter responses with null choices and no error envelope by @ZacharyHampton in https://github.com/pydantic/pydantic-ai/pull/6901
* Inline every `$ref` to a union `$def`, not just the first one by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6960
* Reject unknown `ActivityConfig` keys in `TemporalDurability` by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6964
* Honor per-tool `TaskConfig` on Prefect MCP tools and add `PydanticUserError` to its non-retryable set by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6952
* Pass the unprepared request to the wrapped model in `InstrumentedModel` by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6982
* fix(mcp): inherit agent retries in `MCPToolset.tool_for_tool_def` by @hramezani in https://github.com/pydantic/pydantic-ai/pull/6449
* Fail the workflow on `HookTimeoutError` and `FallbackExceptionGroup` instead of retrying forever by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6978
* Keep thinking alive by not forcing `tool_choice` on OpenRouter `anthropic/` models by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6957
* Add configurable `max_retries` to `ToolSearchToolset` by @pydanty[bot] in https://github.com/pydantic/pydantic-ai/pull/6740
* Fix Temporal `ActivityConfig` validation on Python 3.10 and 3.11 by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6989
* Pass `pydantic_graph` through Temporal workflow sandboxes by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6990
* Memoize Temporal payload `TypeAdapter`s by @DouweM in https://github.com/pydantic/pydantic-ai/pull/7001
* Preserve `SystemPromptPart` semantics across caching and Temporal by @dsfaccini in https://github.com/pydantic/pydantic-ai/pull/6984
### 📦 Dependencies
* Require `genai-prices>=0.1.0` for detailed usage by @alexmojaki in https://github.com/pydantic/pydantic-ai/pull/6933
* Declare `anyio` as a direct dependency of `pydantic-ai-slim` and `pydantic-graph` by @DouweM in https://github.com/pydantic/pydantic-ai/pull/7008

## New Contributors
* @ZacharyHampton made their first contribution in https://github.com/pydantic/pydantic-ai/pull/6901
* @vgrozdanic made their first contribution in https://github.com/pydantic/pydantic-ai/pull/6942
* @rscholz98 made their first contribution in https://github.com/pydantic/pydantic-ai/pull/6858

**Full Changelog**: https://github.com/pydantic/pydantic-ai/compare/v2.21.0...v2.22.0