Add workspace::CloseItemInAllPanes action that closes the active
item's buffer in every pane where it's open, matching Vim's `:bdelete`
semantics. Pane layout is preserved, only the buffer is removed.
`:bd` respects pinned tabs, `:bd!` overrides them and skips save.
Also refactors the tab switcher's close button to use the new
`close_items_with_project_path` method, removing duplicated logic.
Release Notes:
- Vim: `:bd` (`:bdelete`) now closes the file in all panes where it's
open
- Added `workspace::CloseItemInAllPanes` action to close a file across
all panes
Co-authored-by: David Baldwin <baldwindavid@gmail.com>
