Fix editor wheel scrolling over long wrapped lines

[shriram-svg]

Description

Fixes #2104.

Markdown edit mode can lose mouse-wheel scrolling when the wheel event starts over a long wrapped line, such as a fenced code block line over the reported threshold. This adds a small CodeMirror wheel fallback: after a wheel event, if the editor scroller did not move at all, it applies the normalized vertical wheel delta through editor.scrollTo. Native/CodeMirror scrolling still wins whenever it handled the event.

The browser-specific delta normalization is isolated in browser/lib/wheelScroll.js and covered with unit tests.

Issue fixed

• No scrolling in edit mode when a fenced code block contains a long wrapped line (No scrolling in edit mode when code block has any line with over 150 characters #2104).

Type of changes

• 🔘 Bugfix (Change that fixed an issue)
• ⚪ Breaking change (Change that can cause existing functionality to change)
• ⚪ Improvement (Change that improves the code. Maybe performance or development improvement)
• ⚪ Feature (Change that adds new functionality)
• ⚪ Documentation change (Change that modifies documentation. Maybe typo fixes)

Verification

• NODE_PATH=/Users/shriramvasudevan/worktrees/bounties/boostnote-2847/node_modules PATH=/Users/shriramvasudevan/worktrees/bounties/boostnote-2847/node_modules/.bin:$PATH jest tests/lib/wheel-scroll.test.js --runInBand
• NODE_PATH=/Users/shriramvasudevan/worktrees/bounties/boostnote-2847/node_modules PATH=/Users/shriramvasudevan/worktrees/bounties/boostnote-2847/node_modules/.bin:$PATH eslint browser/lib/wheelScroll.js browser/components/CodeEditor.js tests/lib/wheel-scroll.test.js
• git diff --check

yarn lint still fails on the existing baseline, mostly styleName being reported as an unknown React property and unrelated Prettier findings.

Checklist:

• 🔘 My code follows the project code style
• 🔘 I have written test for my code and it has been tested
• ⚪ All existing tests have been passed
• ⚪ I have attached a screenshot/video to visualize my change if possible
• 🔘 This PR will modify the UI or affects the UX
• ⚪ This PR will add/update/delete a keybinding