feat(#258): add chart family style presets

[BorisTyshkevich]

What & why

Extends the existing single Style selector with type-specific Bar, Column,
Area, and Pie presentation presets while keeping advanced combinations in the
Spec editor. Every preset-owned presentation field lives in the canonical
panel.cfg.style object; dormant fields and unknown extensions survive type
switches and the same configuration feeds workbench and Dashboard rendering.

Adds grouped/stacked bars, compact/joined density, additive stacked Area,
Pie/Donut shape, and a reduced-padding Compact Pie frame. Type-specific schema
branches and completion now expose the complete Style contract. Explicit
scale: "auto" resolves to the chart-family default: data range for Line/Area
and zero-based for Bar/Column.

Closes #258

Verification

• npm test — 2,847/2,847 pass; 100% statements and lines
• npm run build — pass (dist/sql.html, 1,208,155 bytes)
• npm run test:e2e — 116/120 pass under the first 10-worker run; four
  unrelated Firefox page.goto startup timeouts before app code loaded
• isolated Firefox rerun of all four affected files with one worker — 15/15 pass

Checklist

• npm test passes (the per-file coverage gate is non-negotiable)
• Tests added/updated in the same change as the code
• npm run build succeeds (single-file dist/sql.html)
• Layers kept honest: pure logic in src/core/, DOM in src/ui/
• No new runtime dependency
• CHANGELOG.md updated
• Reconciled roadmap Roadmap to 1.0.0 #68 and issue Chart-family presentation presets: extend the single Style selector for Bar, Column, Area, and Pie #258 with the final architecture