feat(sdk): propagate chained invoke trace context in START checkpoints

[zhongkechen]

When a new context.invoke() START is checkpointed, the SDK now collects optional plugin metadata and writes the calling operation’s X-Ray header to flat ChainedInvokeOptions.XAmznTraceId. Each invoke in a batched checkpoint carries its own parent span. Existing function, tenant, payload, operation identity and persisted replay outcomes are preserved.

The optional synchronous hook uses readonly SDK-owned input/result types. The collector keeps the first supported nonblank value, warns on conflicting later values and isolates ordinary failures. Both OTel views encode canonical Root/Parent/Sampled, including Sampled=0, without creating an extra span. Checkpointed STARTs do not call the hook again; an uncommitted START may recompute on retry.

Keep this PR draft pending the Lambda model and backend rollout. The SDK implementation assumes the new model field exists, as required by the design. The pinned @aws-sdk/client-lambda 3.1014.0 lacks it: the unchanged wire-model parity guard fails type checking, and the actual generated serializer drops the field. The new serializer regression test intentionally exposes this dependency. After model publication, update/rebase and rerun normal build, installed-consumer, serialization and deployed trace-topology checks. No type suppression, serializer bypass, model gate or test skip is added.

Validation of this revision:

• Core: 1,312 tests pass; the sole failing test is the actual Lambda serializer retaining the new field.
• The 17 new public-wrapper tests cover identity, payload/tenant preservation, absence/error/blank fallback, batched child invokes, pending and terminal replay, and failed-checkpoint retry.
• Both OTel views: 16 propagation tests pass against source, including sampled/unsampled public START paths and exact correspondence to exported calling spans. The supplemental source test configuration bypasses package-build setup only outside the repository; the normal test command is separately verified to stop at the model parity guard.
• OTel type checking, root Biome and diff checks pass. Normal core build/declaration checks fail only at the model parity guard.

Existing registration APIs, provider API version and dependency floors remain unchanged. The declaration compatibility bridge from the earlier draft is retained; earlier released-package/layer checks are historical evidence and must be rerun after the model-dependent build is available. Integrate the coordinated minor PRs #956 and #955 before release. The separate #924 factory migration is not included. Shared CI prerequisite #959 remains in this branch.

The design also proposes DistributedMapOptions.XAmznTraceId; there is no corresponding distributed-map START API in this SDK. Existing map/parallel use CONTEXT operations, and this PR does not invent that future API or its model structures.

Refs #952; backend-dependent end-to-end delivery remains open. Coordinated SDK drafts: aws/aws-durable-execution-sdk-java#768 and aws/aws-durable-execution-sdk-python#755.