Rename all user-facing "mol" references to "molecule" to match the
published binary name (binary: molecule in .goreleaser.yaml):
- root.go: Use string, versionInfo, viper config name, flag descriptions
- init.go: section comment, Short, Long, cfgPath, scaffolded message
- config.go: Long description, Shorts, configFile, WriteFile, Stat check
- molecule_test.go: binary name, version output check, mol.yaml → molecule.yaml
Also fix test helper to use runtime.GOEXE instead of hardcoded /tmp/go/bin/go.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>