Summary

Define and implement a consistent output format standard for all skill scripts.

Problem Statement

Skill output formats are inconsistent, causing issues:

• Issue bug(pr): Get-PRChecks needs a machine-only output mode #639: Get-PRChecks needs machine-only output mode
• Issue bug(pr): Get-PRChecks mixes JSON with human output #632: Get-PRChecks mixes JSON with human output
• Agents cannot reliably parse skill outputs programmatically

Evidence:

• Session 109 export analysis (commit 9b693a5)
• Existing issues bug(pr): Get-PRChecks mixes JSON with human output #632, bug(pr): Get-PRChecks needs a machine-only output mode #639

Requirements

Output Format Standard

• Define JSON schema for skill success/failure responses
• Define format for human-readable output
• Define switching mechanism (-OutputFormat JSON|Human|Auto)
• Document standard in skill development guide

Implementation

• Update GitHubCore.psm1 with output helpers
• Create skill output schema validator
• Migrate existing skills to standard format (phased)

Acceptance Criteria

1. Standard documented in skill development guide
2. Output helpers available in GitHubCore.psm1
3. At least 3 skills migrated to standard format
4. JSON output mode returns only valid JSON (no mixed content)

Priority

P2 - Enhancement (prevents recurrence of #632, #639 pattern)