fix(ios): prevent wrapped text clipping

[CreatlV]

Summary:

Fixes #53450.

React Native can measure wrapped iOS text to a height that becomes one physical pixel too short after layout rounding. The final visual line is then clipped even though TextKit produced it.

#54260 avoided the clipping by adding an epsilon to every measured width and height, but it changed unrelated measurements and was reverted in #54510 after breaking internal tests. This change narrows the adjustment to the existing textDidWrap signal: wrapped text receives one extra physical pixel of height, while width and all non-wrapped measurements remain unchanged.

This follows the narrower approach proposed by @douglowder in #53450 (comment).

Changelog:

[IOS] [FIXED] - Prevent the final line of wrapped text from being clipped

Test Plan:

• Reproduced the issue with the canonical fixture from https://snack.expo.dev/@pekka.soutua/text-cut-off-on-ios on an iPhone 16 Pro simulator running iOS 18.5. Before the change, the target paragraph stopped at “This sente”.
• Applied this wrapped-height-only adjustment and confirmed the complete final line, “This sentence is cut off.”, renders and the following list item moves down by one line.
• Built RNTester from current main, including the modified source file, for the same iPhone 16 Pro / iOS 18.5 simulator destination.
• Ran the repository clang formatter on RCTTextLayoutManager.mm.
• No automated tests were added or run.

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[fabriziocucci]

Picking this up.

Apparently #54260 was reverted shortly after it landed. The revert was triggered by a single internal screenshot test and the evidence points to that being an unrelated flake rather than a real regression from this change.

I'll try to re-land the same fix with two additions:

• A unit test for the pixel-grid rounding that the original change lacked. It covers width and height, in both the on-boundary case (a physical pixel of slack is added) and the sub-pixel case (nothing changes).
• A small RNTester example under the Text screen so the clipping is easy to reproduce and verify.

I am validating it against our internal test suite before landing, I will follow up here once we have some signal.

[fabriziocucci]

Heads up @CreatlV, we re-landed a fix for the wrapped-text clipping in #57698, which also closed #53450, so this should be covered now. So far it's holding and I'll keep an eye on it internally. Thanks for the fix here.