Bun Package Manager

[socgr]

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Implements a new Bun package manager for UniGetUI, covering search,
install, update, and uninstall of Bun-managed packages.

New project: UniGetUI.PackageEngine.Managers.Bun (~430 LOC)

• Bun.cs — manager class (find, get updates, get installed, initialize)
• Helpers/BunPkgDetailsHelper.cs — package details (description, versions, icon)
• Helpers/BunPkgOperationHelper.cs — install/update/uninstall parameters

Integration:

• Registered in PackageEngine.PEInterface (manager enum + native list)
• Icon assigned in Interface.Enums (Bun = '\uE949')
• Settings key BunPreferLatestVersions in SettingsEngine_Names
• Manager toggled in Avalonia settings page (PackageManagerPage.axaml.cs)
• Manager mapped in WinUI settings page (PackageManager.xaml.cs)
• Both .slnx files include the new project

Tests: BunManagerTests.cs (36 tests)

• Package search, installed packages, available updates
• Border-line skipping in outdated-table parsing
• Unicode package name handling
• Local scope rejection (Bun enforces --global only)
• Edge cases: empty results, single-package output, manifest requirements

All 233 package engine tests pass.

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Closes #2519, #4303

Relates to #3506 , #4396

[Gauvain (Gauvino)]

That would awesome !