Format the code, add fmt and check targets

AGENTS.md

@@ -6,6 +6,8 @@
 - `make rpm` - Build RPM package
 - `make podman_rpm` - Build RPM using podman (for MacOS)
 - `make changelog` - Add changelog entry via ./changelog.sh
+- `make check` - Run shellcheck on all shell scripts
+- `make fmt` - Format all shell scripts with shfmt
 - `make clean` - Clean generated files
 - Pre-commit hooks run automatically on commit (see .pre-commit-config.yaml)
 
@@ -14,7 +16,7 @@
 - **File Permissions**: profile.d scripts must be 0644 (install -m 0644) - they are sourced, not executed
 - **Line Endings**: LF only (enforced by pre-commit, see .editorconfig)
 - **No trailing whitespace** (enforced by pre-commit, see .editorconfig)
-- **Error Handling**: Use `command -v` instead of `which` for portability
+- **Error Handling**: Use `command -v` instead of `which` for portability, `set -euo pipefail`
 - **OS Compatibility**: Support both Linux and MacOS with conditional logic
 - **Naming**: Profile.d files use `z-<name>.sh` pattern for alphabetical loading
 - **Licensing**: The Unlicense unless explicitly stated otherwise
@@ -23,8 +25,8 @@
 
 ## Testing
 - No specific testing framework currently used
+- Use `make check` to lint shell scripts with shellcheck
 - Shell scripts should be tested with basic manual verification
-- Use `set -euo pipefail` for robust error handling
 
 ## Cursor/Copilot Rules
 - No specific .cursorrules or .github/copilot-instructions.md found