Fix single candlestick bar visibility by using proper time scale

[Copilot]

Single candlestick bars were invisible on the chart because halfWidth was calculated as _widthPercent (0.25 seconds) instead of scaling it to a meaningful time unit. On charts spanning millions of seconds, a 0.5-second bar is imperceptible.

Changes

• ImplotWrapper::PlotCandlestickOld(): Use 86400.0 * _widthPercent for single bars (1 day base unit)
• ImplotWrapper::PlotCandlestickNew(): Use 86400.0 * _widthPercent for single bars (1 day base unit)

// Before: 0.25 seconds halfWidth → 0.5 second total width (invisible)
const double halfWidth = _count > 1 ? (_bars[1].t - _bars[0].t) * _widthPercent : _widthPercent;

// After: 21,600 seconds halfWidth → 12 hour total width (visible on daily charts)  
const double halfWidth = _count > 1 ? (_bars[1].t - _bars[0].t) * _widthPercent : 86400.0 * _widthPercent;

Multi-bar behavior unchanged.

Original prompt

When i launch the app, the first created bar only appears on the chart when the second bar is on the chart

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[Maxime-Leguevacques]

why this number?

[Maxime-Leguevacques]

@copilot why that number?

[Copilot]

why this number?

86400 is the number of seconds in 1 day (60 × 60 × 24). This chart displays time-based candlestick data where bars typically represent daily intervals. When there's only one bar, we need a reasonable default width - using 1 day as the base unit ensures the bar is visible on daily/weekly charts while matching the typical bar spacing when multiple bars exist.

@copilot why that number?

86400 = seconds in 1 day (60 × 60 × 24). Since this is a time-series candlestick chart where bars represent daily data, using 1 day as the default spacing makes the single bar visible and consistent with multi-bar behavior. The chart setup on line 36 of chartWindow.cpp also uses this time scale (606024*14 for zoom constraints).