Safari: fix incorrect cursor position after smart quote insertion

[jeremy]

Safari 26 positions the cursor incorrectly after smart quotes text substitution, causing it to jump back 1-2 characters.

After insertReplacementText events, the cursor is incorrectly positioned. Trix's selectionDidChange handler syncs, corrupting its internal state.

Hack to work around it:

• Detect whether replacement is "at cursor" (smart quotes) vs "before cursor" (autocorrect) with <= 2 char distance heuristic.
• For at-cursor replacements: manually calculate correct positioning accounting for length diff and triggering character (+1); set cursor in Trix; skip 3 input events to prevent corrupt sync; prevent selectionDidChange from syncing in the meantime; restore cursor position in requestAnimationFrame (no visible cursor movement).

To reproduce the issue: enable Edit > Substitutions > Smart Quotes in Safari, hit Enter twice then "I'll " - including the final space. The cursor should remain after the final space, no after the replaced apostrophe. Similarly with autocorrect: the cursor should not move to the end of the spelling-corrected word.

/cc @rosa

[Copilot]

Pull Request Overview

This PR fixes a Safari 26 bug where the cursor position is incorrect after smart quote text substitution. The cursor incorrectly jumps back 1-2 characters instead of remaining at the expected position after the replacement.

• Implements a workaround to detect "at cursor" vs "before cursor" text replacements using distance heuristics
• Manually calculates and sets correct cursor positioning for smart quotes while preventing Safari's buggy sync
• Adds comprehensive test coverage for smart quotes and autocorrect scenarios

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/trix/models/selection_manager.js	Adds check to prevent selection sync during Safari smart quotes workaround
src/trix/controllers/level_2_input_controller.js	Implements the main workaround logic with cursor positioning calculations and event handling
src/test/system/level_2_input_test.js	Adds three test cases covering smart quotes and autocorrect behavior

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[Copilot]

Pull Request Overview

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull Request Overview

Copilot reviewed 3 out of 4 changed files in this pull request and generated no new comments.

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