chore: remove forked unity web broswer and make it optional

[ImmutableJeffrey]

Summary

• Removed the forked Unity Web Browser implementation that was bundled under com.immutable.passport.
• Kept full Unity Web Browser (UWB) support as an optional integration: if users want the Windows embedded browser, they now install the official UWB packages themselves and the SDK wires into them.

Customer Impact

• Unity Web Browser is now optional and external:

  • Projects no longer get a forked copy of Unity Web Browser “for free” inside the Passport package.
  • To use the Unity Web Browser, customers must:
    • Install the official dev.voltstro.unitywebbrowser package plus the appropriate CEF engine packages. For more details
    • UWB_WEBVIEW is auto-enabled when Unity Web Browser is present.

• If UWB is not installed:

  • Windows behavior falls back to:
    • Throwing a clear PassportException explaining that either UWB must be installed or a custom browser must be provided.
  • Non‑Windows platforms (Vuplex / Gree / WebGL) are unaffected.

• Breaking change for some consumers:

  • Any project that relied on the SDK’s forked UnityWebBrowser folder (engine binaries, scripts, or package IDs under Runtime/ThirdParty/UnityWebBrowser) will need to:
    • Remove those references, and
    • Depend on the official UWB packages instead.

• Sample game still includes UWB by default:

  • It uses the official Unity Web Browser

Added

• New optional runtime assembly Immutable.Passport.Runtime.Uwb that contains all Unity Web Browser–specific integrations:
  • UwbWebView: headless-style bridge used by core Passport when UWB is present.
  • WindowsPassportWebView: Windows IPassportWebView implementation for PassportUI using UWB.
• New editor utility UwbSymbolManager:
  • Detects the presence of the official UWB assembly.
  • Automatically manages the UWB_WEBVIEW scripting define symbol for the current build target group.
• New capability interface IResizablePassportWebView:
  • Allows web views to expose internal resolution control without forcing that API on all IPassportWebView implementations.
  • WindowsPassportWebView implements this to keep its internal UWB resolution in sync with the Passport UI.

Changed

Deprecated

Removed

• Removed the forked Unity Web Browser packages

Fixed

• Removed the forked Unity Web Browser packages

Security

Things worth calling out

Other things to consider:

• Sample app is updated with new SDK changes
• Updated public documentation with new SDK changes (Immutable X and Immutable zkEVM)
• Sample game is updated with new SDK changes
• Replied to GitHub issues