mouse-scroll-multiplier has no effect in v1.2.0 on macOS

[bobrik]

Issue Description

Scrolling speed is no longer controlled by mouse-scroll-multiplier.

Expected Behavior

mouse-scroll-multiplier = 4.0 speeds up scrolling just as it did on v1.1.3.

Actual Behavior

Scrolling has no speed up.

Reproduction Steps

1. Set mouse-scroll-multiplier = 4.0 (or any high value).
2. Run a command with a long output.
3. Try scrolling the output.

Ghostty Logs

No response

Ghostty Version

Ghostty 1.2.0

Version
  - version: 1.2.0
  - channel: stable
Build Config
  - Zig version   : 0.14.1
  - build mode    : builtin.OptimizeMode.ReleaseFast
  - app runtime   : apprt.Runtime.none
  - font engine   : font.main.Backend.coretext
  - renderer      : renderer.generic.Renderer(renderer.Metal)
  - libxev        : kqueue

OS Version Information

macOS 26 (same on 15)

(Linux only) Display Server

None

(Linux only) Desktop Environment/Window Manager

No response

Minimal Ghostty Configuration

mouse-scroll-multiplier = 4.0

Additional Relevant Configuration

No response

I acknowledge that:

• I have reviewed the FAQ and confirm that my issue is NOT among them.
• I have searched the Ghostty repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
• I have checked the "Preview" tab on all text fields to ensure that everything looks right, and have wrapped all configuration and code in code blocks with a group of three backticks (```) on separate lines.

[bobrik]

I forgot to mention: this is when using the trackpad. @rockorager, I suspect it's related to one of your changes.

[00-kat]

I can repro this on Linux too with a trackpad (but not with a mouse).

[onnos]

I can repro as well on MacOS and this (to my own surprise) is so infuriating I downgraded to 1.1.3 for the moment. 😬

[onnos]

Also suspect it is related to #6052.

[mitchellh]

#8670