feat: cancel

[ashenfad]

This PR adds basic task cancellation.

[Copilot]

Pull request overview

This PR adds task cancellation functionality to the agex framework. Long-running tasks can now be gracefully stopped by calling .cancel() on the task wrapper, which writes a cancellation sentinel to the state store that the task loop checks between iterations.

Key changes:

• Added TaskCancelled exception and CancelledEvent for cancellation signaling
• Implemented .cancel() method on task wrappers with cross-process support via raw KV store access
• Added iteration-level cancellation checks in both sync and async task loops

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/agex/test_cancellation.py	Comprehensive test suite covering cancellation scenarios (sync/async, sessions, concurrent execution)
tests/agex/test_agent_state.py	Updated exception type for HTTP host state access from RuntimeError to NotImplementedError
tests/agex/test_agent.py	Removed namespace prefixes from state key references (simplified state access)
docs/api/view.md	Added reference to agent.state() method
docs/api/task.md	Added comprehensive documentation for task cancellation feature
docs/api/state.md	Added reference to agent.state() for accessing state directly
docs/api/agent.md	Added documentation for .state() method with host compatibility table
agex/state/versioned.py	Added set_raw(), get_raw(), remove_raw() methods for bypassing versioned commits
agex/host/modal.py	Implemented state() method for Modal host to enable client-side state access
agex/host/local.py	Implemented state() method for Local host (delegates to resolve_state)
agex/host/base.py	Added abstract state() method to Host base class
agex/agent/task.py	Added cancel() method to TaskWrapper for requesting task cancellation
agex/agent/loop/sync_loop.py	Added cancellation checks at iteration start and removed namespace prefix
agex/agent/loop/common.py	Added check_cancellation() helper and removed namespacing from state initialization
agex/agent/loop/async_loop.py	Added cancellation checks at iteration start and removed namespace prefix
agex/agent/events.py	Added CancelledEvent event type with rich formatting
agex/agent/datatypes.py	Added TaskCancelled exception dataclass
agex/agent/base.py	Updated state() method to use host's state access instead of Local-only restriction
agex/init.py	Exported TaskCancelled and CancelledEvent

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