Cleanup IDE Settings: add search, remove category icons

[Copilot]

The Application Settings window lacked a way to find settings, and category icons added visual noise without aiding navigation.

Search

• New SearchText on ApplicationSettingsViewModel with live filtering (case-insensitive substring match over page/sub-category headers, TitledSetting.Title, and HoverDescription).
• New ISearchableSettingsItem interface + IsVisibleBySearch on SettingsPageViewModel, SettingsCollectionViewModel, and SettingViewModel.
• Sidebar TreeView and right-pane ListBox use ItemContainerTheme to bind IsVisible to IsVisibleBySearch. Individual settings combine search visibility with the existing Setting.IsVisibleObservable via MultiBinding + BoolConverters.And.
• Matching pages auto-expand; selection jumps to the first match only when the currently selected item is no longer visible (preserves explicit sub-category selections).

Category icons removed

• <Image> bindings removed from ApplicationSettingsView.axaml and SettingsCollectionView.axaml (sidebar tree + section headers).
• Icon/IconKey on the VMs are retained and marked [Obsolete]. ISettingsService.RegisterSettingCategory(category, priority, iconKey) signature is unchanged — iconKey is still accepted and resource-resolved, just not rendered.

Usability polish

• Window enlarged to 650×450, sidebar widened to 200px.
• Search TextBox with magnifier glyph (VsImageLib.Search16XMd), "Search settings..." watermark, and UpdateSourceTrigger=PropertyChanged.
• Section headers use a consistent 13px font without leading icon.

// New: live-filter the settings tree
public string SearchText
{
    get => _searchText;
    set { if (SetProperty(ref _searchText, value ?? string.Empty)) ApplyFilter(); }
}

Notes for reviewers

• Full-solution build and running the Studio desktop are blocked in the sandbox by the pre-existing missing VtNetCore.Avalonia submodule; OneWare.Settings and OneWare.Core build cleanly in isolation.
• Debouncing ApplyFilter (suggested in automated review) was left out intentionally — the settings tree is small and the throttle already present on the TreeView's selection side-effects is sufficient.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• av-build-tel-api-v1.avaloniaui.net
  • Triggering command: /usr/share/dotnet/dotnet dotnet exec --runtimeconfig /home/REDACTED/.nuget/packages/avalonia.buildservices/11.3.2/tools/netstandard2.0/runtimeconfig.json /home/REDACTED/.nuget/packages/avalonia.buildservices/11.3.2/tools/netstandard2.0/Avalonia.BuildServices.Collector.dll (dns block)
  • Triggering command: /usr/share/dotnet/dotnet dotnet exec --runtimeconfig /home/REDACTED/.nuget/packages/avalonia.buildservices/11.3.2/tools/netstandard2.0/runtimeconfig.json /home/REDACTED/.nuget/packages/avalonia.buildservices/11.3.2/tools/netstandard2.0/Avalonia.BuildServices.Collector.dll ACCEPT 64990E8E/missingpackages_workingdir cal/bin/git HooksPath (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)