fix(react-ui-core): clamp swipe-back dx to prevent left-drag screen movement

[ENvironmentSet]

Summary

• Fixed a bug in the Cupertino theme swipe-back gesture where dragging left from the edge caused the screen to translate in the negative direction
• Added Math.max(0, ...) clamping to dx in onTouchMove so only rightward drags move the screen
• Left swipes are now fully ignored, matching native iOS behavior

Closes FEP-1995

Test plan

• In a Cupertino theme app, touch the left edge and drag left → screen stays fixed
• Drag right → swipe-back works as expected
• yarn test passes

🤖 Generated with Claude Code

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	stackflow-docs	25690c3	Commit Preview URL	Mar 13 2026, 07:38 AM

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🦋 Changeset detected

Latest commit: 25690c3

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@stackflow/react-ui-core	Patch

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ℹ️ Recent review info

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Run ID: 50414730-32d1-4acd-8320-ea5e6964ef29

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Reviewing files that changed from the base of the PR and between 4d3b294 and 25690c3.

📒 Files selected for processing (2)

• .changeset/fix-swipe-back-direction-lock.md
• extensions/react-ui-core/src/useStyleEffectSwipeBack.ts

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📝 Walkthrough

Summary by CodeRabbit

Bug Fixes

• Fixed swipe-back gesture behavior to prevent unintended left-drag screen movement during touch-based navigation. The fix improves the reliability and consistency of back navigation by ensuring smooth operation without unwanted horizontal displacement, providing a more predictable and responsive gesture-based navigation experience across various mobile devices.

Walkthrough

A patch release for @stackflow/react-ui-core that fixes a bug in the swipe-back gesture handler by clamping horizontal swipe distance calculations to non-negative values using Math.max(0, x - x0), preventing unintended left-drag screen movements.

Changes

Cohort / File(s)	Summary
Release metadata .changeset/fix-swipe-back-direction-lock.md	Changeset documentation for patch version bump describing the swipe-back bug fix.
Swipe-back gesture fix extensions/react-ui-core/src/useStyleEffectSwipeBack.ts	Constrained dx calculation in onTouchMove handler using Math.max(0, x - x0) to prevent negative swipe distances during back gestures.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch swipe-back-direction-lock

📝 Coding Plan

• Generate coding plan for human review comments

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Latest commit:	25690c3
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Preview URL:	https://7e4555d3.stackflow-demo.pages.dev
Branch Preview URL:	https://swipe-back-direction-lock.stackflow-demo.pages.dev

View logs

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• @stackflow/demo

  yarn add https://pkg.pr.new/@stackflow/react-ui-core@685.tgz
  

commit: 38a4abf