docs(skills): add build style skill

.pi/prompts/review.md

@@ -10,8 +10,8 @@ Choose skills from the reviewed files:
 
 - Use the `nix-style` skill for `*.nix` files.
 - Use the `rust-style` skill for `*.rs` files.
-- Use the `rust-style` skill for `Cargo.toml` files.
+- Use the `build-style` skill for `Cargo.toml` files.
-- Use the `rust-style` skill for Bazel files that define Rust targets.
+- Use the `build-style` skill for Bazel `BUILD` files.
 
 If the target includes multiple matching file types, use all matching skills.
 If the target is a diff, choose skills from the changed files.
@@ -35,7 +35,7 @@ Fix: suggested fix
 Keep the code excerpt to one to three lines when possible.
 Use a longer excerpt only when the violation needs surrounding context.
 Use `...` to omit unrelated lines from a multi-line excerpt.
-Use a style-skill rule citation, such as `rust::files.md:23` or `nix::let.md:7`.
+Use a style-skill rule citation in the form `skill::rule-file:line`.
 Make the fix direct.
 Do not include alternatives when one fix best follows the cited rule.
 

.pi/skills/build-style

@@ -0,0 +1 @@
+../../src/skills/style/build

src/skills/style/build/SKILL.md

@@ -0,0 +1,9 @@
+---
+name: build-style
+description: Use when creating, editing, or reviewing Bazel `BUILD` files or Rust `Cargo.toml` package manifests in this repository.
+---
+
+# build-style
+
+Use this skill for Bazel `BUILD` files and Rust `Cargo.toml` package manifests.
+Follow the shared style skill instructions in `src/skills/style/STYLE.md`.

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

@@ -0,0 +1,30 @@
+# Dependency 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 versions keep package manifests consistent with the workspace lockfile.
+
+## Declare Rust dependencies in each build system
+
+### Rule
+
+Declare each direct crate dependency in each build system that builds the Rust target.
+For Cargo, declare the crate in the package `Cargo.toml` file.
+Use `workspace = true` for workspace-managed dependencies.
+For Bazel, add the crate label to the `deps` of the target that uses it.
+Apply this rule to `rust_library`, `rust_binary`, and `rust_test` targets.
+
+### Rationale
+
+Cargo and Bazel resolve Rust dependencies independently.
+Complete declarations keep Cargo, Rust Analyzer, and Bazel builds consistent.

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

@@ -0,0 +1,25 @@
+# Test rules
+
+## Declare Rust tests in Bazel
+
+### Rule
+
+Declare Rust test files in the nearest Bazel `BUILD` file with `rust_test`.
+Do not add `[[test]]` entries to `Cargo.toml` unless the operator explicitly requests Cargo test declarations.
+
+### Rationale
+
+This repository declares Rust test targets in Bazel.
+Keeping test declarations in Bazel avoids duplicate test target lists.
+
+## Use one source input style per `rust_test`
+
+### Rule
+
+Do not set both `crate` and `srcs` on a `rust_test` target.
+Use exactly one input style for each Rust test target.
+
+### Rationale
+
+`rules_rust` rejects `rust_test` targets that set both `crate` and `srcs`.
+Keeping one input style per target makes the test declaration valid and unambiguous.

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

@@ -1,39 +0,0 @@
-# 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
-
-### Rule
-
-Declare Rust test files in the nearest Bazel `BUILD` file with `rust_test`.
-Do not add `[[test]]` entries to `Cargo.toml` unless the operator explicitly requests Cargo test declarations.
-
-### Rationale
-
-Bazel is the source of truth for Rust test targets in this repository.
-Keeping test declarations in Bazel avoids duplicate test target lists.
-
-## Use one source input style per `rust_test`
-
-### Rule
-
-Do not set both `crate` and `srcs` on a `rust_test` target.
-Use exactly one input style for each Rust test target.
-
-### Rationale
-
-`rules_rust` rejects `rust_test` targets that set both `crate` and `srcs`.
-Keeping one input style per target makes the test declaration valid and unambiguous.