Ladda ner GitButler 0.19.8

## Changes
- Adds OpenRouter as a new AI provider in the app
- Adds loading states when squashing and uncommitting
- Conflicted commits now explicitly add a marker in the commit message
- Improved displaying of Pull Request CI/Mergeability state
- Panel resizers in the the app are now easier to grab
- Improved error message propagation when creating branches
- Improved moving of commits across stacks - conflicts are now detected ahead of time
- You can now configure "Kitty" for "open in terminal"
- Improved performance when entering "edit"/"conflict resolution" mode
## Fixes
- Fixes an issue with parsing leading space in directory names
- Fixes a windows fetch/push issue with some alternative SSH clients (e.g. PuTTY)
- Fixes an issue where successful pre-push hooks were incorrectly showing failure
- Fixes an issue with the undo / restore functionality and conflicted commits
- Fixes a GitLab issue with setting the "draft" flag for MRs
## TUI
- The `but tui` subcommand is no longer "hidden" from `--help`
- Adds support for moving hunks
- Adds support for discarding changes
- The details/preview pane can now be resized
- While editing a commit message, the message can be opened in a text editor
- Simplified branch creation (simply pressing b)
- Adds support for easy amending into a selection (shift+r for reverse rub)
- Adds support for invoking any but command with `:`
- Adds branch picker with fuzzy filtering (press t)
## CLI
- GitButler skill - `but skill install` now has an option to install in `.agents`
- Linux: fixes an issue preventing the `but gui` subcommand from opening the GUI correctly