fix(examples-py): validate SageMaker, Semantic Kernel, and Smolagents OTel 2.x spans

[Nightingalelyy]

Summary

• make the SageMaker, Semantic Kernel, and Smolagents example suites preserve one exact shell marker and attach matching run/group metadata
• use bounded semantic workflow inputs/outputs, portable setup, explicit client/Respan teardown, and timeout-aware aggregate runners
• add deterministic failure, streaming, canonical tool, and lifecycle scenarios while retaining credential-gated live behavior where applicable
• run every example against the locally editable Group 25 instrumentation packages

Validation

• Read every current document under respan/contribution/ and audited the complete paired source/example diff against the instrumentation and span contracts
• Example contract tests pass: SageMaker 3/3, Semantic Kernel 4/4, Smolagents 4/4 (11/11)
• Root-scoped Ruff check and format-check pass for all 24 changed example files
• git diff --check passes
• All 12 example processes pass with the repository credentials and exact marker otel2-fix-py-group-25-20260818T071900Z
• Local editable resolution was verified for all three source packages
• Respan MCP audit opened 12 complete trees / 44 full records with one root per trace, exact parents, unique IDs, nonblank grouping, and the exact marker on every record
• Content audit verifies exact usage, SageMaker stream/tool/async behavior, Semantic Kernel canonical definitions and current-turn calls, Smolagents tool names/steps/failure/agent streaming, bounded payloads, privacy, and explicit teardown

External follow-ups

• Platform status/provider/tool convenience-field projections remain as documented in the source PR; the examples do not emit non-contract aliases to work around them.
• Real SageMaker endpoint validation remains skipped unless SAGEMAKER_ENDPOINT_NAME and usable AWS service credentials are configured.

Companion examples

• Source instrumentation PR: fix(instrumentation-py): repair SageMaker, Semantic Kernel, and Smolagents OTel 2.x spans respan#391