Feature Request: Collapsible untracked files section in Git Panel

[n0x29a]

Problem Statement
When working on projects with many generated files (build artifacts, node_modules, temporary files, etc.), the Git Panel can become cluttered with untracked files, making it difficult to focus on the actual changes that need attention. Currently, all untracked files are always visible, which can be overwhelming in projects with extensive .gitignore rules or during active development.
Solution Proposal
I propose adding the ability to collapse/expand the untracked files section in the Git Panel. This would work similarly to how file trees work in the project panel - with a chevron icon that indicates the collapsed/expanded state.
Key features:

Click on the "Untracked" header to toggle visibility of untracked files
Visual indicator (chevron icon) showing the current state
Configurable default state via settings
Keyboard shortcut support for quick toggling

Benefits:

Cleaner Git Panel interface when working with many generated files
Easier to focus on tracked changes and staged files
Preserves the ability to see untracked files when needed
Follows familiar UI patterns from other panels in Zed

Implementation details:

Add collapse_untracked_files_section setting (default: false)
Add git_panel::ToggleUntrackedSection action for keybinding support
Maintain state during the session with option to set default via settings

This is a quality-of-life improvement that would make the Git Panel more usable in real-world projects where untracked files can often outnumber the actual changes developers care about.
What do you think? Would this be useful for your workflow?

#31855