Keep the primary Rust API reference aligned with the qualified installer

[rmcdaniel]

Problem

The public Rust landing is deployed from SDK 2.0.0-rc.38 and its primary API-reference link opens rustdoc for that release, while the same landing’s versionless install command resolves the last qualified public tuple and currently installs 2.0.0-rc.7. The reference therefore advertises APIs such as WorkflowContext::select that are absent from the crate a first-time user is told to install.

Keeping the cross-component tuple pinned until it passes public conformance is correct, but the primary post-install reference must describe that installed artifact. The newest prerelease reference can remain available as a clearly separate surface.

Acceptance criteria

• The versionless Rust install path and the landing’s primary API-reference destination resolve to the same exact SDK release from the public compatibility authority.
• The newest prerelease rustdoc remains discoverable without presenting unqualified APIs as available to users of the qualified installer.
• Existing qualified reference URLs remain usable or redirect to an equivalent version-specific location.
• Deployment qualification reads the public quickstart contract and fails when the primary reference’s crate version differs from the resolver-selected Rust version.
• A first-time-user check installs the resolver-selected crate and compiles the API example reached from the primary reference.

Delete when

Delete when the deployed Rust landing, versionless installer, and primary rustdoc form one exact-version journey and qualification prevents them from drifting again.

[rmcdaniel]

Current status: Deferred to a recorded product milestone

This work is intentionally scheduled for the product milestone recorded in the issue. No maintainer action is pending.