V2/ue/Tools/plan-v2-rust-incremental-build.py minimizes Rust recompilation by
mapping changed files to their owning Cargo package and rebuilding only that
crate plus local reverse dependents. It reuses the crate graph scheduler from
plan-v2-rust-crate-schedule.py, so impacted crates still compile in
topological, critical-path-prioritized waves.
The planner treats Rust source files, Cargo.toml, Cargo.lock, and build.rs
as rebuild inputs. Documentation, target, and node_modules paths are
ignored. Toolchain or cross-linker changes such as rust-toolchain.toml and
V2/ue/Build/Rust/cargo-cross-config.toml force a full graph rebuild.
The release evidence is $(ArchiveRoot)/Rust/incremental-build-plan.json. Horde
gates require rust-incremental-impact-plan-generated and keep the normal
recompile surface at or below 35 percent through
rust-incremental-recompile-surface.