feat: add Workflow Insight instrumentation plugin

[wangyb-A]

Summary

Adds a Workflow Insight instrumentation plugin as a new package,
packages/aws-durable-execution-sdk-python-insight/ — a port of the JS SDK's
workflowInsight() plugin (aws-durable-execution-sdk-js-insight), treated as the
reference implementation throughout. Experimental, matching the JS plugin's status.

It listens to the SDK's instrumentation hooks and emits one curated WorkflowInsight
record (schemaVersion: "1.0") per execution. The wire record keeps the JS camelCase
field names so records read identically across SDKs and land in the same stores/queries.

Behavior (mirrors the JS plugin)

• Exporters: LambdaLogExporter default (one JSON line to the function's log group,
  carrying the name-keyed operationsByName summary) and S3Exporter (the lossless
  per-occurrence operations array; upsert-by-execution-name; none/date/
  function-name partitioning). boto3 is an extra ([s3]) since Lambda provides it.
• Emit model: on-complete / on-failure / on-change with export coalescing —
  a newer record supersedes a pending one; exports never propagate errors into the
  execution.
• Sampling: deterministic per-execution ARN hash; all-or-nothing per execution.
• Content config: input/output omission or transform (redaction), include_errors
  gating operation-level error detail only, per-operation result opt-in with optional
  transform.
• Truncation: phase 1 drops opted-in results oldest-first, phase 2 drops whole
  operations oldest-first, input/output last; per-exporter max_record_size_bytes
  measured against the exact shape each exporter emits.
• Operation detail: top-level (default; children with parentId suppressed) vs
  full-tree; unnamed operations are dropped (JS parity).

Depends on #616 (merged)

The plugin reads InvocationInfo.execution_input / InvocationEndInfo.execution_result
introduced by #616 — the dependency floor is set to >=1.8.0 accordingly (first release
that will carry those hooks). Capability note kept in the module docstring: the operations
map is reconstructed by accumulating per-operation hooks into per-execution state (keyed
by execution ARN to isolate warm-container reuse), since Python hooks carry no
end-of-invocation operations snapshot.

Conformance validation (live, us-west-2)

Validated against the cross-SDK insight conformance suite
(aws/aws-durable-execution-conformance-tests#73, 18 requirements): 18/18 on the s3
sink and 18/18 on the cloudwatch sink. Two known cross-SDK divergences are documented
in that suite rather than patched over here: operation ids pass through the SDK's native
blake2b[:64] format (JS uses MD5[:16]; the suite asserts ids as opaque), and the
per-operation error.name surfaces the customer error class while the record-level error
carries the SDK wrapper name (the suite asserts non-empty).

The suite's Python example handlers land in the conformance repo as a follow-up to #73
once this package is available.

Testing

• 17 unit tests (hatch run test:all packages/aws-durable-execution-sdk-python-insight/tests/)
  covering record shaping, operations indexing, truncation phases, sampling, emit modes,
  and exporter rendering
• hatch fmt clean; package registered in the root known-first-party
• Live conformance runs as above (JS-parity behavior confirmed record-for-record)