feat: add configurable touchpad gestures

[abhighansala]

Configurable Touchpad Gestures

This change adds the compositor-side foundation for configurable touchpad gestures in COSMIC.

What changed

• Added a configurable TouchpadGestures structure to cosmic-comp-config.

• Added separate gesture configurations for 3-finger and 4-finger swipes.

• Added configurable actions for:

  • App Library

  • Workspace Overview

  • Previous Workspace

  • Next Workspace

  • Window Switcher

  • Window Switcher Previous

  • None

• Updated gesture handling in cosmic-comp to resolve actions from the configured finger count and swipe direction.

• Added 3-finger gesture support:

  • Swipe Up → App Library

  • Swipe Left → Window Switcher Previous

  • Swipe Right → Window Switcher

• Preserved the existing 4-finger workspace and Workspace Overview behavior.

• Added App Library surface detection alongside the existing Workspace Overview detection.

• Reused the existing COSMIC system actions for Window Switching, App Library, and Workspace Overview instead of implementing duplicate functionality.

• Added layout-aware defaults so existing horizontal and vertical workspace behavior remains compatible.

• Changed gesture capture so all gestures with 3 or more fingers are tracked by the compositor.

Default gesture mapping

Gesture | Default action -- | -- 3-finger Up | App Library 3-finger Down | None 3-finger Left | Window Switcher Previous 3-finger Right | Window Switcher 4-finger Up | Workspace Overview 4-finger Down | Workspace Overview 4-finger Left | Previous Workspace 4-finger Right | Next Workspace

The cosmic-settings UI for editing these mappings will be implemented separately.

Verification

The changes were verified with:

git diff --check
cargo check
cargo build --release

All checks completed successfully.

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