Add gRPC client and worker connection resiliency

[berndverst]

Summary

• Add public gRPC resiliency option types and shared transport helpers, then wire them through core and Azure Managed constructors.
• Harden worker, sync client, and async client connection recovery to better survive silent disconnects, transport failures, and channel recreation scenarios.
• Add focused regression coverage plus user-facing changelog and design/plan updates for the new resiliency behavior.

Test Plan

• Focused pytest run covering grpc resiliency, worker resiliency, worker concurrency loop, client resiliency, and Azure Managed wrapper wiring.
• flake8 on all changed source and test files.

[Copilot]

Pull request overview

Adds first-class gRPC connection resiliency to the Durable Task Python SDK (core durabletask/) and threads the new configuration through Azure Managed wrappers, with extensive regression tests and design docs.

Changes:

• Introduces GrpcWorkerResiliencyOptions / GrpcClientResiliencyOptions and shared internal resiliency helpers (backoff, failure tracking, transport-failure classification).
• Updates worker stream loop and sync/async clients to detect transport-shaped failures and safely recreate/retire SDK-owned channels while preserving caller-owned channel semantics.
• Adds comprehensive unit tests (core + azuremanaged) plus docs/specs and changelog entries.

Reviewed changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
durabletask/worker.py	Implements worker stream monitoring, backoff, failure tracking, and safe SDK-owned channel retirement with in-flight tracking.
durabletask/client.py	Adds sync/async unary invocation wrappers and SDK-owned channel recreation + retirement handling.
durabletask/grpc_options.py	Adds public resiliency option dataclasses with validation.
durabletask/internal/grpc_resiliency.py	Adds shared backoff, FailureTracker, and transport-failure classification helpers.
durabletask-azuremanaged/durabletask/azuremanaged/client.py	Forwards client resiliency options through Azure Managed client wrappers.
durabletask-azuremanaged/durabletask/azuremanaged/worker.py	Forwards worker resiliency options through Azure Managed worker wrapper.
tests/durabletask/test_worker_resiliency.py	New worker resiliency tests (silent disconnect, graceful close, recreation thresholds, in-flight close deferral).
tests/durabletask/test_grpc_resiliency.py	New tests for option validation, backoff, FailureTracker, and transport-failure classification.
tests/durabletask/test_client.py	Adds sync/async client channel recreation/retirement tests and wrapper verification.
tests/durabletask/test_worker_concurrency_loop.py	Updates tests to call prepare_for_run() before reusing the worker manager.
tests/durabletask/test_worker_concurrency_loop_async.py	Updates async loop tests to call prepare_for_run() before reusing the worker manager.
tests/durabletask-azuremanaged/test_azuremanaged_grpc_resiliency.py	New tests validating Azure Managed wrapper pass-through of resiliency options.
CHANGELOG.md	Documents new resiliency options and behavior changes in core SDK.
durabletask-azuremanaged/CHANGELOG.md	Documents pass-through resiliency options in Azure Managed package.
docs/superpowers/specs/2026-04-23-grpc-resiliency-design.md	Adds design spec for resiliency behavior and public API.
docs/superpowers/plans/2026-04-23-grpc-resiliency.md	Adds implementation plan document for the work.
.gitignore	Ignores .worktrees/ and normalizes coverage.lcov entry formatting.