Document Rust stable activity identity and downstream idempotency keys #396

Current state: delivered all8 Rust guides plus all8 execution-guarantees service paragraphs. PR397 mergebd33ba31c9e2ce222decc640a104a6ec1f94afae; exactCI39973236140/artifact39977452931/actualPages39978971911 PASS. All16 live routes/navigation/fullmetadata/accessor rows/copiedhelper/48 exact-source paragraphs and12 mobiletheme views verified. Published normal4.9 receiptSDK139/6367230500 final; no tuple promotion/shared218 checkpoint closure.

Rust activity code needs a stable logical activity identity for downstream deduplication, together with its owning workflow instance and run for correlation. The Rust portion of shared .github#211 is published in SDK4.9.0, including normal installed and actual Server controls.

Product review: these accessors are an accepted product capability, now implemented and qualified by SDK #139 / PR #140. Website guidance describes that delivery; it does not substitute an external ledger recipe for resumable activity checkpoints under shared .github#218. Website #272 remains the closed wrapper pointing to that separate requirement.

Acceptance:

• Publish English plus all seven translated Rust guides, with identical executable helper bytes and updated reviewed-source hashes. Require actual installed Rust4.9 or newer; the separately selected older installation tuple remains unchanged.
• Explain immutable original activity_execution_id, workflow_id (workflow instance), and run_id, all optional received identities. Logical activity identity spans retries; a per-attempt task/attempt ID is not a fallback idempotency key.
• Show a handler deriving a namespaced downstream key and explicitly refusing a missing activity identity before any effect. Authors can instead provide an explicit stable business key. The example itself does not perform a payment or guarantee exactly-once external effects.
• Preserve actual local/session/older-Server/Server-free boundaries. Local callbacks can have real parent workflow/run IDs but have no Server activity identity before their command is recorded. Worker-session callbacks expose their normal claim identity. Missing fields remain None.
• Add service-scoped prose and a link to the Rust example in all eight execution-guarantees guides; keep language-specific code on the Rust page. Link the delivered guide from Clarify heartbeat progress versus resumable activity checkpoints #272 while preserving shared Bind the local Server quickstart to loopback explicitly #218 as unfinished product work.
• Verify exact-head checks, Sonar findings, actual Pages publication and all eight live routes before Website delivery. No Server, Cloud, other-SDK, selected-tuple or checkpoint product closure follows.

Release evidence: source/tag 93d3c3aa78be4347045f50833ffcdc02dcabc4ed, normal registry/archive/lock SHA256 be21bb5b033cc8db364f1f9e3d789607eb6eff976126965cfc95072146c220a6; OIDC39967443675 and API39967624766 succeed. Website independently checked the registry/archive/VCS identity, all70 Rust-source/README files, HTTP200/version4.9 and the published accessor anchors. The SDK owner compiled and ran the exact proposed helper SHA256 5bc0013b04c501791ebee8d5768fe5d7ac744c853ff58cc2c6b6ca4a807e16c0 in its normal installed Rust1.86 graph. No duplicate compiler/runtime or source overlay is introduced.