docs: add Rust agent guidance

[jan-kubica]

Summary

• add shared Rust agent guidance for strict workspace lints, Dylint, Bon builders, artifacts, and parity testing
• add a shared modeling guideline for avoiding boolean flags where a named state/domain type is more durable

[gemini-code-assist]

Code Review

This pull request introduces a comprehensive set of Rust coding, testing, and side-effect guidelines in modules/rust.md, and updates modules/engineering.md to advise against using boolean fields for growing states. The review feedback correctly identifies a contradiction in the Rust guidelines regarding enums and boolean options, suggesting an update to align with the general engineering guidelines and prevent boolean blindness.

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[chatgpt-codex-connector]

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Reviewed commit: eebb10aa9b

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[chatgpt-codex-connector]

Run Dylint with all targets and features

In Rust workspaces that put stella Dylint checks on tests, examples, or feature-gated code, this narrower command only runs through cargo check defaults, while the baseline Clippy gate above explicitly covers --all-targets --all-features. Dylint accepts Cargo check args after -- (its docs show cargo dylint --all -- --all-targets ...), so this shared guidance should mirror the same target/feature coverage; otherwise CI can pass while custom lints never inspect those code paths.

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