The `--output yaml` flag was accepted but aliased to JSON since
printYAML() was never defined. Add printYAML() using gopkg.in/yaml.v3
(already an indirect dep via viper) and split all output format
branches into explicit json/yaml/table paths.
Affected commands: workspace list/create/inspect/audit,
agent list/inspect/peers, platform audit/health.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>