## Discover Nix files

### Rule

Use `util.collectNixFiles` to discover Nix files.
Do not use `builtins.readDir` with a `.nix` suffix filter for this purpose.
Pass `util` to Nix functions that need the helper.

### Rationale

`util.collectNixFiles` centralizes recursive discovery of Nix files.
Repository Nix code uses one implementation.

## Remove Nix file suffixes with the utility

### Rule

Use `util.removeNixSuffix` to derive a Nix name from a path.
Do not call `lib.removeSuffix ".nix"` outside the utility definition.

### Rationale

The utility centralizes Nix file-name normalization.

## Use executable helpers for package commands

### Rule

Use `lib.getExe` when invoking a package's main executable.
Use `lib.getExe'` when invoking a non-main executable from a package.
Do not build executable paths with `"${pkg}/bin/name"` when an executable helper can name the target.
Use `lib.getExe' config.programs.<name>.package "tool"` when a command must follow a configured package option.

### Rationale

Executable helpers use the package output that contains binaries.
They also make package ownership explicit.
`lib.getExe'` avoids accidentally resolving a package's main executable when code needs a different tool.

## Prefer NixOS package ownership for commands

### Rule

Use `pkgs.<name>` for Home Manager tools.
Use `config.programs.<name>.package` when a NixOS module owns the selected package.
Do not read `config.home-manager.users.<user>.programs.<name>.package` for command paths.

### Rationale

Home Manager uses the NixOS package set in this repository.
Referencing `pkgs.<name>` avoids needless dependency paths through the Home Manager user tree.
Configured NixOS package options preserve the selected package when a module owns the tool.