Command Result and status --json tracer

[BramVR]

Parent

#70

What to build

Introduce a Command Result module plus Presentation adapters by making status the first tracer. status should return one command result shape that can render both current human output and stable JSON, with exit classes separated from prose.

Acceptance criteria

• status keeps current human output compatibility unless docs are intentionally updated.
• status --json returns a stable machine-readable shape with diagnostics and readiness state.
• Command Result carries an exit class independent of renderer.
• Tests cover human output, JSON output, and exit class behavior.
• Command Catalog and status command docs mention the runnable JSON flag.

Blocked by

• Shared Readiness Decision for existing commands #72