Context

Fixes a regression where typing a space in the Git Panel's "Switch Branch" picker would make no response at all instead of inserting the character. The same picker in the title-bar Git Switcher was unaffected.

Root cause: PopoverMenu links the opened menu's focus handle into the parent element's dispatch tree so that contains_focused returns true on the parent while the popover is open. GitPanel::dispatch_context uses
contains_focused to decide whether to add the ChangesList key context, so that context is active while the branch picker is open. Because Picker and Editor have no binding for a bare space, dispatch fell through to
the "GitPanel && ChangesList" binding, which maps space to git::ToggleStaged, consuming the keystroke before it could reach the text input.

The fix narrows the context guard to "GitPanel && ChangesList && !GitBranchSelector",
so those bindings are skipped whenever the branch picker (or any other GitBranchSelector context) is focused inside the panel.

The same change is applied to the vim keymap, which would have similarly intercepted k,
j, x, and other letter keys typed in the picker, this behavior was observed in #52617 and I made the same fix in #52687

Closes #52771 and potentially #52617

Video of the manual test of the fix below :

How to Review

• assets/keymaps/default-linux.json, default-windows.json,
  default-macos.json, vim.json : identical one-line change in each: I added && !GitBranchSelector to
  the "GitPanel && ChangesList"
  . No Rust changes needed.

Self-Review Checklist

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Release Notes:

• Fixed space and other keys being swallowed when typing in the Git Panel branch picker