feat: detect inconsistent line-height values in CSS audit

[fracergu]

Summary

• Audit step now collects every line-height declaration and font: …/<lh> shorthand, clusters near-duplicates against a canonical scale, and flags unitless-vs-px mixing
• New field lineHeights in AuditReport (found, suggestedScale, unitlessMix)
• Wired through UserDecisions → buildResolvePrompt so the resolve step uses audited line-heights as a starting point
• Chaos score gains +1 when unitlessMix is true

Before vs After — AuditReport shape

Before

{
  "brand": "", "chaosScore": 1, "summary": "...",
  "colorClusters": [...], "fonts": [...],
  "spacing": { "found": [...], "suggestedScale": {...}, "nonScaleValues": [...] }
}

After

{
  "brand": "", "chaosScore": 1, "summary": "...",
  "colorClusters": [...], "fonts": [...],
  "spacing": { "found": [...], "suggestedScale": {...}, "nonScaleValues": [...] },
  "lineHeights": {
    "found": [1.2, 1.25, 1.5, 1.75],
    "suggestedScale": { "tight": 1.2, "snug": 1.25, "normal": 1.5, "relaxed": 1.75 },
    "unitlessMix": true
  }
}

Real-world validation

The full pipeline was validated end-to-end against a real LLM (DeepSeek V4 Flash) using DEEPSEEK_API_KEY. Sample CSS with mixed unitless line-heights produced:

audit.lineHeights.found: [1.2, 1.5, 1.6, 1.75] → resolve.tokens.typography.lineHeights: {"tight": 1.2, "normal": 1.5, "relaxed": 1.75}

How to test

1. Paste any CSS with line-height declarations into the playground or run npx mint-ds audit ./path
2. Check that the audit report now includes lineHeights
3. Resolve tokens and verify typography.lineHeights appears in mint-ds.tokens.json
4. Export to any target — line-heights should be present in the generated output

Checklist

• npx tsc --noEmit passes with no errors
• Tested with real CSS input through the full audit → tokens → export flow
• UI is responsive on mobile (tested at 375px width) — no UI layout changes, only data flow
• No new Spanish strings introduced — all user-facing text is English
• No hardcoded colors or values that should be CSS variables