Structured error output

[8bitAlex]

Current errors are human-readable strings. Agents need machine-parseable errors to pivot and recover.

Proposed format

{
  "error": {
    "code": "REPO_NOT_CLONED",
    "message": "Repository 'api-gateway' is not cloned locally",
    "repo": "api-gateway",
    "hint": "Run `raid install` to clone all repos in the active profile"
  }
}

Requirements

• Stable error code enum (documented)
• Human-readable hint field for terminal users
• Distinct exit codes for error categories:
  • 0 success
  • 1 generic failure
  • 2 config/validation error
  • 3 task execution failure
  • 4 network/clone failure
  • 5 not-found (repo, profile, task)
• Errors emitted as JSON when --json flag is active

Acceptance criteria

• Error code enum defined and documented
• Exit code table in README
• JSON errors match the schema from Issue Add build and test badges to README #2
• Existing error sites refactored to use structured errors
• Error code enum is treated as semver-stable: codes never renamed or repurposed across minor versions; new codes additive only