chore(release): v0.2.0-beta.1

[Shewart]

First beta of ShellUI.Native.CLI.

Changes

• Version 0.2.0-beta.1 (Directory.Build.props, README badge)
• Release notes: the 18 new components (button-group, input-group, menubar, command, navigation-menu, data-table, chat, form, image-viewer, prev-next-nav and the charts), the change-events rule (user input only, breaking), CLI and theme additions, upgrade steps and known limitations
• Fix: update includes the shell utility. init wrote Shell.cs without recording it, so update shell said it wasn't installed and update --all left it out; an app made with 0.1.0-alpha.2 couldn't get the chart colors. init now records shell, and update treats a component whose file exists as installed
• Fix: pie-chart's description no longer mentions donuts (donut-chart is its own component)
• Docs: counts in the roadmap and PLAN.md (81 families, 112 CLI targets), release checklist in the plan

Verification

• Each commit builds and passes its tests on its own; 1462 tests; dotnet format clean; the release notes extract with scripts/extract-release-notes.sh
• Each new component, plus sheet and label, installed alone into a fresh Avalonia and a fresh dotnet new maui app (Windows), and all 115 entries together in one app per platform: 0 warnings / 0 errors
• An app set up with 0.1.0-alpha.2 takes button-group, date-range-picker and bar-chart after update shell button, or update --all, and builds 0/0 on both platforms
• The packed tool, installed from the .nupkg: reports 0.2.0-beta.1, list shows donut-chart, fresh Avalonia and MAUI apps build 0/0