feat: add amc score summary command

[thewisecrab]

Difficulty: Medium
Expected outcome: Add amc score summary that runs all scoring modules and produces a single-page overview:

• Overall maturity level
• Per-dimension scores
• Top 3 strengths and weaknesses
• Recommended next actions

This would be the 'executive summary' view.

Files to edit: src/cli.ts, possibly new file src/diagnostic/scoreSummary.ts