Add HStack renderable item culling tests

[honghaoz]

Motivation

• Bring HStack test coverage in line with VStack by verifying renderableItems(in:) correctly culls offscreen children and includes children that are moved into the query rect via offset.

Description

• Added two tests to ComposeUI/Tests/ComposeUITests/ComposeNodes/HorizontalStackNodeTests.swift: test_renderableItems_filtersOffscreenChildren and test_renderableItems_includesOffsetChildren.
• test_renderableItems_filtersOffscreenChildren lays out a 3-child HStack and asserts that only the child overlapping the query rect is returned by renderableItems(in:).
• test_renderableItems_includesOffsetChildren applies an offset to a child and asserts the offset child is included when its frame intersects the query rect.

Testing

• No automated tests were run as part of this change.

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Codex Task

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Note

Improves HStack coverage for renderableItems(in:) behavior.

• Adds test_renderableItems_filtersOffscreenChildren to ensure only overlapping children are returned
• Adds test_renderableItems_includesOffsetChildren to ensure offset children intersecting the query rect are included

^{Written by Cursor Bugbot for commit 543de0d. This will update automatically on new commits. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.74%. Comparing base (fb9776c) to head (543de0d).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master       #3   +/-   ##
=======================================
  Coverage   88.74%   88.74%           
=======================================
  Files          90       90           
  Lines        4346     4346           
=======================================
  Hits         3857     3857           
  Misses        489      489           

Flag	Coverage Δ
ComposeUI	88.74% <ø> (ø)

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