refactor(skills): group Rust build rules

src/skills/style/rust/rules/build.md

@@ -1,4 +1,18 @@
-# Bazel rules
+# Build rules
+
+## Use workspace dependency versions
+
+### Rule
+
+Declare Rust dependency versions in the repository root `Cargo.toml` under `[workspace.dependencies]`.
+Reference workspace dependencies from package `Cargo.toml` files with `workspace = true`.
+Do not declare dependency versions in package `Cargo.toml` files unless the operator explicitly requests a package-local version.
+Add package-local dependency features only when the feature set is specific to that package.
+
+### Rationale
+
+The repository has one Cargo workspace and one `Cargo.lock`.
+Centralized dependency versions keep package manifests consistent with the workspace lockfile.
 
 ## Declare Rust tests in Bazel
 

src/skills/style/rust/rules/cargo.md

@@ -1,15 +0,0 @@
-# Cargo rules
-
-## Use workspace dependency versions
-
-### Rule
-
-Declare Rust dependency versions in the repository root `Cargo.toml` under `[workspace.dependencies]`.
-Reference workspace dependencies from package `Cargo.toml` files with `workspace = true`.
-Do not declare dependency versions in package `Cargo.toml` files unless the operator explicitly requests a package-local version.
-Add package-local dependency features only when the feature set is specific to that package.
-
-### Rationale
-
-The repository has one Cargo workspace and one `Cargo.lock`.
-Centralized dependency versions keep package manifests consistent with the workspace lockfile.