chore: update commitlint subject-case rule to allow sentence-case #43

Problem

The current commitlint.config.js enforces strict lower-case for commit subjects:

'subject-case': [2, 'always', 'lower-case'],

This causes valid commits with proper acronyms (CLI, API, SQL, etc.) to fail CI. For example, PR #42 fails with:

⧗   input: docs: restructure quickstart with sbx CLI as primary path
✖   subject must be lower-case [subject-case]

Context

• Conventional Commits spec only mandates lowercase for the type field, not the subject
• Acronyms like CLI, API, SQL are proper nouns that should remain capitalized per technical writing standards
• The current rule forces incorrect capitalization ('cli' instead of 'CLI')

Proposed Solution

Update commitlint config to use sentence-case which allows proper nouns and acronyms while maintaining structure:

'subject-case': [2, 'always', 'sentence-case'],

Or alternatively, allow multiple cases:

'subject-case': [2, 'always', ['sentence-case', 'lower-case']],

Consensus

This was reviewed by a 3-agent consensus vote (architect, security, scope-steward) with 100% approval:

• Improves readability without weakening enforcement
• Aligns with Conventional Commits spec (which doesn't mandate lowercase subjects)
• Low risk, high value configuration fix

Related

• Blocks: docs: restructure quickstart with sbx cli as primary path #42 (docs restructure PR)
• Blocks: docs: restructure quickstart user journey with sbx CLI as primary path #41 (docs restructure issue)

Testing

# After change, this should pass:
echo "docs: restructure quickstart with sbx CLI as primary path" | npx commitlint