[iOS] Skip no-op ellipsis recolor in processTruncatedAttributedText

[cezarywojcik]

Summary:

RCTTextLayoutManager processTruncatedAttributedText: matches the truncated (ellipsis) range's color attributes to the character before it, so a truncated line's "…" doesn't carry a foreground/background color from the trimmed text (added in fcb6cdc / #39408). It does this by unconditionally removing and re-adding NSForegroundColorAttributeName/NSBackgroundColorAttributeName over the truncated range on every draw. That storage edit invalidates the layout TextKit just computed and re-typesets the paragraph inside drawAttributedString: — even when the attributes are already correct, which is the case for every single-color <Text numberOfLines={...}>.

This is expensive during continuous layout (e.g. resizing a split-view pane on iPad, where every visible row redraws per frame). On an iPad Pro (M5), Release build, ~20 ellipsized rows: an Instruments Time Profiler trace showed 72.8% of the paragraph draw-path cost inside this method's forced re-typeset (2.29s of a 3.15s draw path over the session). With the skip, observed p95 frame time during pane resizes dropped from 66ms to 42ms and worst frame from 100ms to 66ms, with identical rendering.

The change: before editing, check whether the truncated range already uniformly carries the attribute found at characterRange.location - 1, and skip the remove/add when it does. Multi-color truncated lines keep the existing recolor behavior, preserving #39408.

Related: #58101 defers the same edit out of the line-fragment enumeration to fix a crash with composed characters; this skip composes with that change (both reduce how often the storage is mutated mid-draw).

Changelog:

[IOS] [FIXED] - Avoid re-typesetting truncated single-color Text on every draw by skipping the no-op ellipsis recolor

Test Plan:

• Manual, iPad Pro (M5) + iPhone, Release: single-color and multi-color truncated <Text numberOfLines={1}> and multiline numberOfLines={3}, light/dark — rendering identical before/after; ellipsis color matching for multi-color text (the 【iOS】Fixes ellipsis carries background from trimmed text #39408 case) still applies.
• Instruments: with the skip, no _fillLayoutHole... re-typeset stacks under -[RCTParagraphTextView drawRect:] for single-color truncated text; unchanged behavior for multi-color text.
• Perf numbers above from a production RN 0.86 app (frame-time probe around a divider drag re-laying out ~20 ellipsized rows per frame).

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