Add focused candle scrubbing

[brandtnewlabs]

Summary

• add scrub.dimTarget: "otherCandles" so the candle under the finger keeps its full up/down colors while every other candle body and wick dims
• add configurable scrub.dimFadeMs (60 ms by default, 0 for instant) and keep the focused render on the UI thread by reusing the existing batched candle paths with a clipped full-strength pass
• hide the scrub guide and selection dot in focused-candle mode, remove the candle demo's time tooltip, and leave volume unchanged
• preserve standard line-chart scrubbing when a chart switches modes without rewriting its otherCandles config
• update the candle scrub demo, public types/JSDoc, guide, API reference, changelog, and regression coverage

Why

Focused candle scrubbing gives the touched OHLC bar a clear visual priority without adding another positional marker. The configurable, short opacity transition keeps the interaction responsive while avoiding a hard visual snap.

Validation

• npm run typecheck — passed
• npm run lint — passed
• npm test -- --runInBand --silent — 99/99 suites passed; 1,530 passed and 5 skipped
• npm run verify — typecheck and lint passed; its parallel Jest phase reproduced repository resource-saturation timeouts in 4 otherwise-passing suites, all of which passed in the serial full run above
• React Doctor — 96/100, unchanged; only the existing Expo route options export warning
• agent-device QA — iPhone 17 Pro simulator: focused colors, dim/release animation, no scrub line/dot/time tooltip, and return-to-live behavior verified
• React profiling — 0 React commits during a 15.1 s scrub interaction