feat: add pinch-to-zoom support to editor

[gahanad]

Description

Adds pinch-to-zoom support to the editor to make editing more convenient on mobile devices.

Users can adjust the editor's font size using a two-finger pinch gesture, improving readability and usability on smaller screens.

Changes Made

• Added a pinch-to-zoom extension for the editor.
• Dynamically adjusts the editor font size based on the pinch gesture.
• Enforces minimum and maximum font-size limits.
• Saves the updated font size setting when the gesture ends.
• Cleans up touch event listeners when the extension is destroyed.
• Added unit tests covering pinch-zoom behavior and font-size calculations.

Testing

• Added unit tests for pinch-zoom functionality.
• Verified the targeted unit tests pass.
• Manually tested pinch-to-zoom on an Android device.
• Verified the full test suite and CI checks.

Related Issue

Closes #2426

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; both numbered previous findings are fixed.

Summary

Adds two-finger pinch zoom to the editor, with bounded font sizes, live previews, and saving when the gesture ends.

• You can pinch the editor text to change its font size.
• Two-finger gestures cancel pending text-selection actions.

_{Reviews (6) · Last reviewed commit: "Fixed corrections for pinchZoom" · Reviewed by Greptile}

[bajrangCoder]

There several accidental zoom in/zoom out

screen-20261011-164227.mp4

[gahanad]

@greptile

[bajrangCoder]

Touch events keep targeting the element where each finger first landed, even after that element is removed from the DOM. Since move/end/cancel are only listened for on contentDOM, the gesture can get stuck:

1. Two fingers start on lines in the lower part of the editor; spread to ~2x.
2. The preview font change + requestMeasure() makes CM recompute a smaller viewport (visible area + ~500px margin), and the .cm-line under a finger is unmounted.
3. That finger's touchmove/touchend now dispatch to a detached node and never reach contentDOM.

Result: gesture.pinching stays true, the inline preview is never cleared or persisted, and every subsequent two-finger touchstart bails on if (gesture.pinching ...) — pinch is dead until the editor state is swapped.

Suggest attaching the move/end/cancel listeners to window/document (capture) when a pinch starts and removing them in endPinch/destroy.

[bajrangCoder]

Also isn't the line number area and editor area pinch-to-zoom at same time for better and smooth feel? as currently line number area adjusted itself after leaving zoom.

Also in some cases some accidental scrolls maybe using three finger/two finger etc does nothing but normally in acode those just scrolls so removing that will be a bit weird(if there is no valid reason)