Render the crown-only reward shape

[LandynDev]

Counterpart of allways #557: reward = eligible × pool × crown × cap × fill.

• ScoreBreakdown renders the single formula; volShare stays as a trailing informational value
• scoreSlices deleted; the history chart becomes a single reward band (no crown/execution stack, separator, second edge, exec labels/legend/tooltip rows)
• rateQuality dropped from the API model; formula strings updated (model comment, CrownHistoryPanel header)

Build green (tsc + vite).