Fix durabletask issues surfaced during Azure Functions investigation

[andystaples]

Summary

While building out Azure Functions support, several pre-existing issues in the core durabletask SDK were surfaced. This PR splits those fixes out into a dedicated, self-contained change so they can be reviewed independently of the larger Functions work.

Fixes (durabletask/worker.py)

• Timer timezone bug — Timers created with a timezone-aware fire_at were compared against the orchestration's naive UTC clock, which could cause them to fire at the wrong time. Timezone-aware fire times are now normalized to naive UTC before scheduling.
• Orchestration version presence check — Replaced a truthiness check on executionStarted.version with HasField("version"). A singular protobuf message field is always truthy, so the version was being set on OrchestrationContext even when none was provided.
• genericEvent handling — Replaying a genericEvent history event (for example, the marker the Durable Functions extension appends when rewinding an orchestration) raised OrchestrationStateError. Such informational events are now ignored during replay, matching the .NET worker.
• Lock-granted entity events — Over the legacy entity protocol, a lock-granted response attempted to deserialize an empty operation result and raised. Lock-granted events no longer attempt result deserialization.

Additions

• Task.result — New read-only property aliasing Task.get_result() (durabletask/task.py).
• bind_context / clear_context — Now exported from durabletask.extensions.history_export for managing the ambient history-export context.

Serialization robustness (default wire format unchanged)

• ScheduleState.from_json gains an optional converter parameter plus a _rebuild_configuration helper so the nested ScheduleConfiguration round-trips under alternate converters (durabletask/scheduled/models.py).
• ScheduleOperationRequest gains explicit to_json / from_json hooks, mirroring the plain dataclass field mapping so the wire format is unchanged for the default JSON converter while remaining serializable by converters that require an explicit hook (durabletask/scheduled/orchestrator.py).

Validation

• Pylance clean; flake8 clean on all changed files.
• CHANGELOG.md updated with ADDED / FIXED entries for the user-facing changes.
• Full core test suite: 734 passed, 9 skipped.

[Copilot]

Pull request overview

This pull request fixes several correctness issues in the core durabletask worker that were surfaced while investigating Azure Functions support, and adds a couple of small API/serialization improvements to improve interoperability with alternate JSON converters.

Changes:

• Fixed multiple replay/runtime edge cases in durabletask/worker.py (timer timezone normalization, orchestration version presence check, ignore genericEvent during replay, and avoid deserializing empty lock-grant results in the legacy entity protocol).
• Added a Task.result read-only property as an alias for Task.get_result().
• Improved scheduled-entity JSON round-tripping under non-default converters (explicit hooks and converter-aware rebuild logic), and exported ambient history-export context helpers.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
durabletask/worker.py	Fixes replay/runtime bugs (timers, version presence, generic events, legacy entity lock results).
durabletask/task.py	Adds Task.result property aliasing get_result().
durabletask/scheduled/orchestrator.py	Adds explicit to_json/from_json hooks for ScheduleOperationRequest to support converters that can’t serialize bare dataclasses.
durabletask/scheduled/models.py	Makes ScheduleState.from_json converter-aware and adds a helper to reliably rebuild nested ScheduleConfiguration.
durabletask/extensions/history_export/init.py	Re-exports bind_context / clear_context in the public module surface.
CHANGELOG.md	Documents user-facing additions and fixes under ## Unreleased.