feat: add TrueSheetPeek component

[lodev09]

Summary

Adds a new TrueSheetPeek wrapper component that marks part of the content as the sheet's peek content. Its natively-measured height is included in the peek detent height (along with the header and footer heights), so the collapsed size follows the actual content — no onLayout juggling.

<TrueSheet detents={['peek', 0.9]} initialDetentIndex={0}>
  <TrueSheetPeek>
    <BookingSummary />
  </TrueSheetPeek>
  <BookingDetails />
</TrueSheet>

• New TrueSheetPeekView Fabric component (iOS/Android) that measures via native layout and reports to the sheet's detent calculator — no JS round trip
• Registers with the nearest container: subtree search when content mounts (Fabric mounts bottom-up), self-attach walk-up for late mounts, detach on unmount
• Peek detent height = header + peek + footer, 150 fallback unchanged
• Web mirrors it via onLayout + context feeding the vaul snap point
• Docs note that TrueSheetPeek belongs at the top of the content (the sheet reveals from the top; only its height is used)
• MapScreen example now uses ['peek', 'auto', 1] with the heading as peek content

Type of Change

• New feature

Test Plan

• yarn typecheck, yarn lint, yarn test (44 passed)
• Example app MapScreen on iOS/Android: initial present at peek detent sizes to header + heading, resizes live when peek content changes

Checklist

• I tested on iOS
• I tested on Android
• I tested on Web
• I updated the documentation (if needed)
• I added a changelog entry (if needed)

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Project	Deployment	Actions	Updated (UTC)
react-native-true-sheet	Ready	Preview, Comment	Jul 11, 2026 8:38pm