feat: charts for MAUI and Avalonia

[Shewart]

Adds a chart family for MAUI and Avalonia, drawn by the components themselves (MAUI's GraphicsView, Avalonia's Render) with no charting package.

Changes

Theme

• ShellToken.Chart1–Chart5 in both themes, on MAUI and Avalonia and in the theme resource file, converted from ShellUI's --chart-1–--chart-5. Charts take their series colors from them

Charts

• chart: shared core used by every chart: series model, axes with rounded tick values, legend, tooltip under the pointer, 600 ms grow-in animation, redraw on data or theme change, and a small canvas interface each platform implements
• bar-chart: grouped, stacked or horizontal bars, negative values
• line-chart: smooth or straight lines, optional dots
• area-chart: overlapping or stacked areas
• pie-chart: PieChart and DonutChart, with a value and label in the hole
• radar-chart: a shape per series on a ringed grid
• radial-chart: concentric progress rings with a center value
• Series values and labels can be written in XAML as comma-separated lists (Values="1, 2, 3")
• The drawing code is the same on both platforms: curves and arcs become point lists, so a canvas only draws lines, polygons and text

Also

• Registry: 114 entries, 111 CLI targets, 80 families; every chart depends on chart
• Demos: a Charts category in MAUI and a Charts section in Avalonia, ten examples each
• Docs: Charts chapter and token table in COMPONENTS.md, roadmap (P7 done), plan
• Fix found on the way: MAUI's text measurement on Windows is tighter than the drawn glyphs, which clipped chart labels; text is now drawn into a roomy box with the platform's own alignment

Upgrade note

This changes shell. A project whose shell came from an older CLI version needs shellui-native update shell before it adds a chart. This goes into the next release notes, with update button (for button-group) and update calendar (for date-range-picker).

Verification

• Solution builds 0 warnings / 0 errors on all four MAUI targets; 1083 tests pass; dotnet format check clean
• bar-chart alone, radial-chart alone and all seven together in a fresh Avalonia app, and all seven in a fresh dotnet new maui app (Windows), build 0/0
• Both demos checked in dark and light: every chart type, hover (cursor band, hover dots, grown slice, tooltip), adding a series and replacing values from code, theme switch
• Hit tests return the expected category, slice or ring on both platforms; the animation runs about 30 frames over ~610 ms, and IsAnimated="False" draws at once

Not included

• Zoom and pan, mixed bar and line charts, click events on a bar or slice

Not tested

• Real pointer hover on MAUI (hover was driven through the component), touch, Android, iOS and Mac Catalyst (they compile), macOS and Linux, large data sets