M9.T1: CLI JSON Schema Contracts

[flyingrobots]

Phase A1 — Contract Lockdown

Deliverables

• docs/contracts/cli/*.schema.json for every --json command:
  • status.schema.json
  • diff.schema.json
  • doctor.schema.json
  • review.schema.json
  • suggest.schema.json
  • export.schema.json
  • import.schema.json
  • nodes.schema.json
  • at.schema.json
• docs/contracts/CLI_CONTRACTS.md — human-readable contract documentation
• schemaVersion field in every JSON output
• CI validation: every --json command output validates against its schema

Acceptance Criteria

• Every --json command validates against schema in CI
• Backward-incompatible changes fail CI unless semver major flag is set
• schemaVersion present in all JSON outputs

Part of M9 — IRONCLAD GA