CLI command three-concern boundary

Chose the project buildCommand() async-generator boundary over direct Stricli builders, command-defined json flags, stdout.write(), or flags.json branches because the wrapper owns authentication, telemetry, global flags, rendering, and filtering. Commands yield CommandOutput(data) and may return { hint }; human and JSON output consume the same data. Human output always injects --fields; --json is injected unless already defined. ALWAYS_STRIP flags, including log-level, never reach command functions.