[zhongkechen]

The sampling guide describes changing decisions and application persistence without defining which policies durable traces support. Define the two supported modes for both views: an authoritative upstream decision, or deterministic sampling from the stable canonical trace ID with configuration unchanged across retries and reinvocations.

Explain why Sampled=1 overrides local always_off and ratio policies for durable spans, exclude non-deterministic local policies when no authoritative upstream decision exists, and clarify that in-memory caching is not durable persistence. Configuration and troubleshooting now link to the shared contract.

Part of #295. Merge this guide first so the new shared-contract link is available, then merge the coordinated OTel README updates:

• JavaScript: docs: clarify supported OpenTelemetry sampling policies aws-durable-execution-sdk-js#1132
• Java: docs(otel): define supported sampling modes aws-durable-execution-sdk-java#852
• Python: docs: define supported OTel sampling modes aws-durable-execution-sdk-python#885

Keep #295 open until all four documentation updates land.

This focused change overlaps the broader guide rewrite in #302. Retain the supported sampling modes section and its anchor when combining the changes.

Validation:

• Repository-wide Markdown formatting, spelling, and hidden-character checks passed.
• Zensical 0.0.40 production build completed with no issues; the sampling section was checked in a local browser preview.
• All 687 example references and vendored asset checks passed; generated HTML heading, list, and local fragment links verified.
• git diff --check passed. Documentation only; no runtime or cloud tests required.