Go Module Implementation

- Root go.mod at repository root (monorepo/workspace style)
- Single gomod2nix.toml at root (generated via: gomod2nix generate)
- Apps are subpackages (e.g., apps/stackpanel-go)

Generated files (package.json, .air.toml, tools.go) are created as
derivations, ensuring hermetic builds with proper dependency ordering.
Files are materialized via stackpanel.files system during shell entry.

- Packaged app with buildGoApplication (for distribution)
- Development environment with mkGoEnv (for go run/test/build)
- Derivation-based file generation (hermetic, can be build dependencies)
- File materialization via stackpanel.files for IDE/tooling support
- Test package for flake checks

stackpanel.apps.stackpanel-go = {
  path = "apps/stackpanel-go";  # Path relative to repo root
  go = {
    enable = true;
    binaryName = "stackpanel";  # Rename binary (optional)
    ldflags = [ "-s" "-w" ];    # Optional linker flags
    generateFiles = true;       # Generate package.json, .air.toml, tools.go
  };
};

- packages.<name>: Built Go binary (with generated files if enabled)
- packages.<name>-dev: mkGoEnv for development
- packages.<name>-generated-files: Derivation with generated files
- checks.<name>-tests: Go tests

Generated files are materialized via stackpanel.files.entries.
Use `write-files` command to manually regenerate files.
Files are automatically written on shell entry.