feat: CLI digest command — human-readable summary to stdout

[jpleva91]

Problem

sentinel_analyze.py writes a long markdown file. Need a quick CLI summary for terminal output.

Acceptance Criteria

• python sentinel_analyze.py <job> --digest prints a 10-line summary
• Summary includes: score, delta from previous, top 3 failure types, top 3 near-misses, regressions
• Exit code 0 if score improved, 1 if regressed

Hints

• The data is already computed in analyze_job() — just need a compact formatter
• Useful for CI integration and /evolve automation

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