AWS SFN: open real-cloud parity gaps #1473

cloudemu's SFN emulation still differs from real AWS in the ways listed below. Each item is a separate fix, so pick any one and open a PR for it against development. Comment here with the item you're taking so two people don't work on the same one.

Check the expected behaviour against the AWS API reference and the real CLI or SDK. A good fix goes in the provider (providers/aws/...) so the Go library and cloudemu serve behave the same, and adds a test that fails before the fix. See CONTRIBUTING.md for setup.

High

• Non-Lambda Task integrations (sqs/sns/dynamodb/ecs/states:startExecution/.sync) unsupported (providers/aws/sfn/asl/task.go:119 "only Lambda is supported")
• Activity-ARN Task fails instead of dispatching to GetActivityTask pollers (same task.go guard)
• RedriveExecution on SUCCEEDED execution not rejected (ExecutionNotRedrivable) (executions.go RedriveExecution has no status check)
• RedriveExecution does not re-run; flips to SUCCEEDED leaving stale error/cause (executions.go RedriveExecution sets Status=SUCCEEDED unconditionally (metrics branch only adds emission))

Medium

• .waitForTaskToken callback pattern unsupported
• Missing intrinsics (MathAdd, ArrayLength, ArrayContains, Base64, Hash, JsonMerge, StringSplit...) fail executions (asl/intrinsics.go has only Array/ArrayGetItem/Format/JsonToString/StringToJson/UUID; merges report correctness #5)
• StartSyncExecution accepted on STANDARD state machine (executions.go StartSyncExecution no type check)
• No LambdaFunctions*/ActivityRunTime-style integration metrics (split from SFN-09; not in metrics branch sfn/metrics.go)
• SFN terminal status event not emitted/verified under --async-settle
• Missing CloudWatch metrics: Step Functions Version/Alias dimensioned metrics

Low

• Distributed Map ItemReader (S3 input) not supported
• LoggingConfiguration accepted but no log delivery to CloudWatch Logs (no log sink in providers/aws/sfn)
• StopExecution on terminal execution returns original stopDate (needs re-verification)