Add instance ID prefix orchestration queries

[andystaples]

Summary

• add instance_id_prefix to OrchestrationQuery and serialize it to InstanceQuery.instanceIdPrefix
• cover protobuf serialization and in-memory query filtering
• document the public query filter

Validation

• python -m pytest tests/durabletask/test_batch_actions.py
• python -m flake8 durabletask
• python -m flake8 tests/durabletask

[Copilot]

Pull request overview

Adds a new public query filter to the core SDK to allow querying orchestrations by an instance ID prefix, wiring it through gRPC request serialization and validating behavior via tests and changelog documentation.

Changes:

• Added OrchestrationQuery.instance_id_prefix as a public filter option.
• Serialized the new filter to InstanceQuery.instanceIdPrefix in build_query_instances_req.
• Added tests for serialization and in-memory backend filtering; documented the new API in CHANGELOG.md.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
tests/durabletask/test_batch_actions.py	Adds orchestration query-by-prefix test and serialization regression test.
durabletask/internal/client_helpers.py	Populates InstanceQuery.instanceIdPrefix from OrchestrationQuery.instance_id_prefix.
durabletask/client.py	Extends the public OrchestrationQuery dataclass with instance_id_prefix.
CHANGELOG.md	Documents the new user-facing query filter under ## Unreleased.

Suppressed comments (1)

durabletask/client.py:199

• OrchestrationQuery is a public dataclass; inserting instance_id_prefix in the middle changes the positional argument order, which can break callers that instantiate OrchestrationQuery positionally. To preserve backwards compatibility, append new fields at the end of the dataclass field list.

    instance_id_prefix: str | None = None
    # Some backends don't respond well with max_instance_count = None, so we use the integer limit for non-paginated
    # results instead.
    max_instance_count: int | None = (1 << 31) - 1
    fetch_inputs_and_outputs: bool = False

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[Bernd Verst (berndverst)]

Requesting changes for the positional-constructor compatibility regression. The wire mapping and query behavior otherwise look sound.

[andystaples]

Resolves one half of #222

[Bernd Verst (berndverst)]

Second-pass review complete at c71cec2. The positional constructor and existing class-pattern order are preserved, both provider changelogs now cover the inherited API, and the existing protobuf field is wired through the shared sync/async request path without client-side filtering. Targeted tests, affected-file Flake8, and strict core/Functions Pyright checks pass.