[lexical] Bug Fix: Skip ZWSP insertion for format mismatch on Android Chrome

[mayrang]

Description

On Android Chrome, Samsung Keyboard and other non-Gboard keyboards (Yandex, FUTO) cache the composing region internally. When a user toggles bold/italic during composition, $handleCompositionStart detects a format mismatch between selection.format and node.getFormat() and inserts a ZWSP via CONTROLLED_TEXT_INSERTION_COMMAND. This DOM mutation triggers Samsung Keyboard's restartInput(), which restores the cached composing text and causes duplication.

The original issue (#7649) reports text duplication after toggling format on Samsung Keyboard. On our Android device the duplication didn't reproduce on the current main, but a related symptom did: typing Korean with bold enabled on Samsung Keyboard splits jamo (e.g. typing "한글" produces "ㅎㅏㄴㄱㅡㄹ" with each consonant/vowel separated). The root cause is the same — the ZWSP insertion disrupts Samsung's composing region tracking.

Fix

Guard the format and style mismatch conditions with !IS_ANDROID_CHROME so the ZWSP insertion is skipped on Android Chrome. The other conditions that trigger ZWSP (element anchor, non-collapsed selection, ANDROID_COMPOSITION_LATENCY timing heuristic) remain unguarded since those handle structural cases unrelated to Samsung's caching behavior.

The trade-off: toggling format during an active composition on Android Chrome Samsung Keyboard won't show the format change visually until the composition ends. The format itself is preserved correctly — selection.format persists through the composition cycle and applies on the next insertText.

Closes #7649

Test plan

• pnpm vitest run --project unit — all pass, no regression.
• pnpm tsc --noEmit clean.
• New unit test LexicalAndroidChromeComposition.test.ts:
  • Format mismatch with IS_ANDROID_CHROME: true does not dispatch CONTROLLED_TEXT_INSERTION_COMMAND.
  • Element anchor still dispatches CONTROLLED_TEXT_INSERTION_COMMAND (guard doesn't leak to other conditions).
  • Test fails on main, passes with fix (verified by stashing the change and running against original code).
• Manual Android Chrome (Samsung Keyboard):
  • Tap Bold → type Korean "한글": jamo compose correctly (no separation into "ㅎㅏㄴㄱㅡㄹ").
  • Type "hello" → tap Bold → type "world": no duplication, "world" appears once.
  • Gboard unaffected (Gboard handles restartInput gracefully).

[vercel]

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Project	Deployment	Actions	Updated (UTC)
lexical	Ready	Preview	Jul 2, 2026 6:40am
lexical-playground	Ready	Preview	Jul 2, 2026 6:40am

[etrepum]

This is slightly shorter if the conditions are fused (suggestion won't pass ci-check cleanly without running prettier first)

Suggested change

	(!IS_ANDROID_CHROME && node.getFormat() !== selection.format) ||
	(!IS_ANDROID_CHROME &&
	$isTextNode(node) &&
	node.getStyle() !== selection.style)
	(!IS_ANDROID_CHROME && (node.getFormat() !== selection.format ||
	$isTextNode(node) &&
	node.getStyle() !== selection.style))

[mayrang]

Done, pushed in 37da33f.