Keep development command JSON machine-readable

[adrianwebb]

Objective

Prevent local setup, verification, source-schema builds, and host activation progress from contaminating --json stdout.

Acceptance

• One-shot development operations capture subprocess output.
• SDK source-schema preparation does not write build chatter to command stdout.
• Host activation and guest-image export suppress progress and child output in JSON mode.
• Live source-check invocation pipes successfully through jq.
• Full CLI suite passes.

Evidence

Gate	Result
CLI tests	182 passed
live JSON source use	parsed successfully