feat(ios): expose UIGlassEffect clear variant via new backgroundGlass prop

[michelemarri]

Closes #663

Adds a new backgroundGlass?: 'regular' | 'clear' prop on <TrueSheet> so apps can opt into iOS 26's UIGlassEffectStyleClear variant. Naming mirrors the existing backgroundColor / backgroundBlur props per your suggestion in the issue thread.

API

<TrueSheet detents={[0.5, 0.9]} backgroundGlass="clear">
  {/* ... */}
</TrueSheet>

• 'regular' (default): existing behavior — system-default Liquid Glass (.regular style, with luminosity veil for content legibility)
• 'clear': new option → UIGlassEffect(style: .clear, isInteractive: true). High transparency, minimal adaptivity, designed for media-rich backdrops where the app provides its own dimming/blur layer

Precedence

Follows the existing pattern — backgroundColor wins over backgroundBlur, which wins over backgroundGlass. The new prop only kicks in when neither of the other two is set, on iOS 26.1+, and UIDesignRequiresCompatibility is not opted-in.

Scope

• src/fabric/TrueSheetViewNativeComponent.ts — Fabric spec
• src/TrueSheet.types.ts — public TS types (new BackgroundGlass type + prop)
• src/TrueSheet.tsx — destructure + forward to native
• src/navigation/types.ts — add to TrueSheetNavigationSheetProps Pick list
• ios/TrueSheetViewController.h — new @property
• ios/TrueSheetView.mm — wire newProps.backgroundGlass → _controller.backgroundGlass
• ios/TrueSheetViewController.mm — use it in setupBackground

~40 lines added, zero deletions. Fully additive: no behavior change for existing users, default 'regular' preserves current Liquid Glass appearance.

Testing

Deployed in production via patch-package in soglia72 (an Italian fantasy-football app for Serie A). The backgroundGlass="clear" variant is used on a sheet presented over a custom animated pitch canvas, where the system's regular glass veil was washing out the background. No regressions on existing sheets that don't set the prop.

Happy to add docs / changelog entry / example snippet if you'd like — let me know how you prefer to structure additions. Thanks for the library and the quick turnaround on the issue!

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[lodev09]

Hey @michelemarri, thanks for the PR! Looks good to me.
Have you tried building on android? I think this will break, we need a stub for this on android, I think.

Also if you don't mind updating the CHANGELOG. Thank you!