chore: prepare Python minor releases

[zhongkechen]

Prepare the Python nonbreaking OTel minor release by bumping the testing package from 1.2.1 to 1.3.0. Scoped PR #758 fixes callback update delivery and empty-error history round trips in testing package runtime code, so those fixes need a new testing artifact. This PR contains only the version bump; unmerged fixes are release prerequisites and are not cherry-picked here.

Package	Latest PyPI	Prepared release
SDK	2.0.1	2.1.0, already set on main by #753
OTel	1.0.0	1.1.0, already set on main by #753
Testing	1.2.1	1.3.0, this PR

The existing Lambda layer SDK pin is already 2.1.0. Production dependency floors remain unchanged. Following RELEASING.md, the intended combined tag is sdk-v2.1.0,otel-v1.1.0,testing-v1.3.0, created only after the release changes are merged and all publication gates pass.

Draft release notes

aws-durable-execution-sdk-python v2.1.0

Already merged: reject competing OTel views before discovered factories run, with explicit opt-in validation and cleanup (#753). Configurations enabling both views must select one before upgrading the coordinated SDK 2.1/OTel 1.1 pair.

Pending: handler-worker OTel context propagation (#756) and callback terminal notification delivery/replay corrections (#758).

aws-durable-execution-sdk-python-otel v1.1.0

Already merged: correct operation/retry status mappings (#752), enforce one view with SDK 2.1 and recover log enrichment after rejected-instance reuse (#753).

Pending: first-invocation sampled fallback-root export (#754), handler context propagation (#756), and expanded replay/status/user-callback conformance checks (#758 and aws/aws-durable-execution-conformance-tests#131).

aws-durable-execution-sdk-python-testing v1.3.0

Pending scoped fixes: report callback success/failure/timeout through UpdatedOperationIds, consume checkpoint-delivered updates while retaining newer changes, and preserve empty-error history round trips (#758). Main also contains virtual-clock, per-execution worker and local chained-invoke improvements since the published 1.2.1 artifact.

Release gates

• Merge fix(otel): export sampled fallback roots early #754, fix: run invocation lifecycle on handler worker #756, test: cover OTel replay and status mappings #758 and test: cover OTel replay, status and user callback contexts aws-durable-execution-conformance-tests#131. Keep the breaking factory migration refactor(plugin): create one plugin instance per invocation #737 and service-model-dependent feat(plugin): propagate chained invoke trace context in START checkpoints #755 outside this release.
• Reconcile the current fix: run invocation lifecycle on handler worker #756/test: cover OTel replay and status mappings #758 compatibility contracts. At f225d880, fix: run invocation lifecycle on handler worker #756's actual OTel metadata requires core >=2.1.0 and removes the optional handler_context design; test: cover OTel replay and status mappings #758 at a6c8c904 still has that design and core >=2.0.0. This preparation preserves main's dependency floors and does not claim old-core compatibility for the unmerged redesign.
• Obtain green CI on the final main commit. Main ef683592 currently fails plugin conformance case 10-18, with missing middle-resume WAIT hook records despite backend success; the root cause is unconfirmed.
• Resolve the unconditional Insight entry in the existing PyPI publisher before publishing. Insight 0.0.1 is not on PyPI, so this would attempt an out-of-scope initial publication. This PR changes neither Insight nor the publisher.
• Merge the version bump, refresh against final main, rebuild artifacts, and finalize release notes/tag checks under RELEASING.md.

Validation

On main ef683592 plus this one-line version change, using the publisher's Hatch 1.16.5 and Python 3.13.15:

• Built wheels and source distributions for all four entries in the live publisher matrix, including Insight for preflight inspection only.
• Verified artifact versions, unchanged production dependencies, Python minimums, LICENSE/NOTICE files, the OTel wheel dependency contract and combined-release layer pin resolution.
• 18 existing package-metadata, layer-version and wheel-contract tests pass; testing-package Hatch formatting and git diff --check pass.

These checks validate release preparation, not the unmerged fixes or final release commit. No release, tag, package, layer or merge is created by this PR.