Epic: Add a stable machine-readable integration protocol

[delaudio]

Goal

Expose a stable, versioned machine-readable protocol for editor and GUI integrations without requiring consumers to parse human-oriented tables or terminal output.

Principles

• Keep existing human-readable output and interactive behavior unchanged.
• Make structured output explicit through --json, --format json, or --format jsonl.
• Emit structured payloads on stdout and diagnostics on stderr.
• Include a protocol schemaVersion in every payload.
• Define stable error codes and exit-code semantics.
• Never include resolved secret values or credential material.
• Preserve Hum's daemonless architecture.
• Keep product and project policy outside the Hum codebase.

Planned work

• Define versioned JSON success and error envelopes #34
• Add machine-readable project, template, and service discovery #32
• Add JSON output for service status #35
• Add JSON output for doctor diagnostics #33
• Add bounded JSON Lines output for logs and follow mode #36
• Document protocol compatibility and publish Hum 0.5.0 #37

Recommended order: protocol envelope, discovery/status/doctor/logs in parallel, then documentation and release.

Exit criteria

• A consumer can discover registered projects, templates, and services using structured output.
• A consumer can obtain service status and diagnostic results using structured output.
• A consumer can follow logs as bounded JSON Lines events.
• Success and error payloads have documented, fixture-tested schemas.
• The protocol ships in a tagged Hum release with compatibility documentation.