fix(aws-lambda): attribute parallel history events to their states

[user-github-me]

When parallel Step Functions branches interleave, the Lambda progress reader assigns every completion/failure to the latest entered state. A chunk completed after a different branch is entered loses its frame count, and its failure is reported under that unrelated state.

Carry the enclosing state through each event's previousEventId chain. Use that state for chunk frame counts and Lambda failures, retain the fallback for histories without parent IDs, and report <unknown> when an explicit parent is missing.

Validation:

• 151 AWS tests pass across 13 files; all eight new attribution regressions fail on main.
• Coverage includes optimized and raw Lambda events, interleaved success/failure, pagination, unrelated-task frame counts, missing parents, and existing sequential histories.
• Package build/typecheck, root lint, changed-file formatting, test reachability, and commit hooks pass.
• Built SDK on Node 22 with the workspace tsx loader: four local HTTP paginated-history probes pass for success/failure in both integration formats.

No cloud deployment was used; verification uses the SDK's existing client-injection boundary.\n

[jrusso1020]

Thanks. In the shipped state machine, each chunk Map iteration contains a single RenderChunk task, and nothing else runs while the Map is in progress. Interleaved events therefore always come from the same state name, and the current attribution is already correct. The interleaving in these tests can't happen with this stack, so we'll pass on this one. — Rames