Align Rust release documentation with the general-first SDK landing

[rmcdaniel]

Problem

The Rust SDK landing is now correctly useful without Cloud access: it leads with the public crate, generated API reference, and general SDK guide, while presenting Durable Workflow Cloud as a secondary limited-early-access option.

The published 2.0.0-rc.12 README still puts “Start with Rust Cloud” before the local first run, does not identify Cloud there as limited early access, and says the Rust landing leads to the Cloud quickstart even though the landing intentionally does not. The generated API reference inherits that README. The 2.0.0-rc.12 changelog likewise says the landing leads with the Cloud quickstart before the API reference.

These contradictory public surfaces make the deployment-mode hierarchy depend on which Rust entry point a user opens.

Acceptance criteria

• The repository README and generated API documentation present the generally available Rust install, local/self-hosted path, and API reference without implying that Cloud is the universal first run.
• Cloud guidance remains discoverable but is clearly identified as a secondary, limited-early-access deployment path.
• Descriptions of the Rust landing match its deployed general-first navigation and do not claim that it leads with the Cloud quickstart.
• The changelog accurately describes the final documentation hierarchy shipped for the release.
• Publish the corrected README in the next sequential Rust SDK prerelease; do not alter the immutable 2.0.0-rc.12 tag.
• Add focused consistency qualification that protects the deployment-mode hierarchy without coupling tests to exact prose, headings, or Markdown layout.

Delete when

Delete when the corrected source, live generated reference, and next published crate README agree on the general-first hierarchy and Cloud’s limited-access status.