feat(component): add number formatting to single value and tooltips - #169

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@component/src/charts/chart-utils.ts`:
- Around line 79-83: The current items.map callback builds a label using
`${p.marker ?? ""} ${p.seriesName ?? ""}: <b>${val}</b>` which can produce "
undefined: <b>…</b>" or an extra colon/space when seriesName is missing; update
the template in the items.map (the arrow callback that assigns lines) to only
include the colon and seriesName when p.seriesName is present (e.g.
conditionally prepend `${p.seriesName}: ` or omit it), and ensure spacing around
p.marker (p.marker) is trimmed or added only when needed so the final string
never shows "undefined" or stray punctuation while still using formatNumber(val,
tooltipConfig) for value formatting.

In `@component/src/components/composed/chart-options-schema.ts`:
- Around line 373-375: The tooltip decimalPlaces option is currently inert
because tooltipFormatOptions (which includes decimalPlaces) is spread into the
chart option registries but the chart components (bar-chart.tsx, line-chart.tsx,
pie-chart.tsx) use hardcoded tooltip configs; either remove tooltipFormatOptions
from the bar/line/pie arrays or wire the formatter: call
buildTooltipFormatter(...) inside each component and replace the hardcoded
tooltip config with one that uses the returned formatter (ensure you
import/accept decimalPlaces from props and pass it to buildTooltipFormatter in
bar-chart.tsx, line-chart.tsx, and pie-chart.tsx so decimalPlaces controls
tooltip output).

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Nitpick comments:
In `@component/src/charts/chart-utils.ts`:
- Around line 32-41: The formatting branches for "comma" and "compact" are using
hardcoded locales ("en-US" and "en"); update NumberFormatConfig to accept an
optional locale string (e.g., locale?: string) and use that value when
constructing toLocaleString/Intl.NumberFormat, falling back to a sensible
default (like navigator.language or "en-US") when locale is undefined; adjust
the "comma" case and the "compact" case to reference the new config.locale
instead of the hardcoded strings so formatting respects the caller's locale
preference.