[kvlonge]

Why

Fensu’s Rust analyzer now supports Python-authored custom rules over versioned, analyzer-owned facts. Authors need the callback, fact, policy, routing, and cache contracts documented alongside the Rust analyzer.

Changes

• document typed custom Rust File rules and standard target configuration
• describe ctx.rust workspace, crate, file, item, and resolved-use facts
• explain project rules, shared policy semantics, native-only routing, parse reuse, and subject-aware caching
• add the Rust fact models and availability boundary to the RuleContext reference

Verification

• compared examples and claims with fensu PR #81
• independent complete-diff documentation review completed; its routing wording finding was corrected
• git diff --check
• public-repository hygiene scan