[Bug]: Dead-key apostrophe inserts extra quotes in the composer #16859

Area

apps/web, including the Linux desktop composer.

Steps to reproduce

1. Use a keyboard layout where the apostrophe key is a dead key for accents.
2. Type s in the composer with the caret at the end and no selected text.
3. Press the single-quote key once, then Space to commit a literal apostrophe.
4. Type il.

Expected behavior

The composer contains s' after step 3 and s'il after step 4. Accented letters should continue to compose normally.

Actual behavior

The composer contains s'´' after step 3, then s'il' after step 4. Accented letters work normally; committing an apostrophe is the broken case.

Impact

Frequent incorrect text when writing French with a dead-key keyboard layout.

Version and environment

Linux x64 desktop, 0.0.46-nightly.20261007.2774, also present in main at 611132c171f3a821bd2e32f22261135cef6330ac.

Investigation

The composer's handleTextInput treats any nonempty replacement range as selected text to surround with delimiters. ProseMirror can report a replacement range covering a provisional dead-key accent while the current editor selection is empty. Surrounding that accent with ' produces exactly s'´', then selects the accent so subsequent typing leaves a trailing apostrophe.

A focused test mounting the actual controlled ComposerPromptEditorTiptap in jsdom reproduces s'´' in both plain and rich-text modes when replaying this replacement. This is a replay of the editor's text-input boundary, not a native Linux keyboard-event capture.

Existing issues and PRs were searched for a duplicate. This report is specifically about committing a literal apostrophe, rather than accent composition or Markdown grave accents.