v0.3.1

Changed

• Upgraded the lean-rs workspace crates (lean-rs-worker-protocol, lean-toolchain) to 0.2.2 and bumped the Lean
  toolchain pin to leanprover/lean4:v4.31.0-rc2 (header-identical to -rc1).
• RoleFeatures.factsFromStatement now deduplicates role features in O(n) via a hash set on the (injective) feature
  sort key, replacing the previous per-insert linear scan (O(n²) in a statement's feature count). The emitted feature
  rows are byte-identical — featuresJson/sortedFeatures re-sort by the same key, so only the distinct set, not
  insertion order, was ever observable — so the change is a pure performance fix with no cache-key or version impact.
  (runtime_source_digest updated for the source edit.)