feat(options): add 'winpinned' to pin a window #39157

Problem:
- Unable to "pin" a window to prevent closing without specifically
  being targeted.
- :fclose closes hidden windows (even before visible windows).

Solution:
- Add 'winpinned' window-local option. When set, window is skipped by
  :fclose and :only. Pin the ui2 cmdline window (which should always be
  visible), so that it is not closed by :only/fclose.
- Skip over hidden (and pinned) windows with :fclose.

Co-authored-by: glepnir <glephunter@gmail.com>

runtime/lua/vim/_core/ui2.lua

@@ -130,6 +130,8 @@ function M.check_targets()
           hl = 'Normal:MsgArea'
         elseif type == 'msg' then
           hl = search_hide
+        elseif type == 'cmd' then
+          api.nvim_set_option_value('winpinned', true, { scope = 'local' })
         end
         api.nvim_set_option_value('winhighlight', hl, { scope = 'local' })
       end)

runtime/lua/vim/_meta/options.gen.lua

@@ -8324,6 +8324,16 @@ vim.o.wmw = vim.o.winminwidth
 vim.go.winminwidth = vim.o.winminwidth
 vim.go.wmw = vim.go.winminwidth
 
+--- If enabled, the window is pinned and will not be closed by `:only`
+--- and `:fclose`. Only commands specifically targeting the window can
+--- close it.
+---
+--- @type boolean
+vim.o.winpinned = false
+vim.o.wp = vim.o.winpinned
+vim.wo.winpinned = vim.o.winpinned
+vim.wo.wp = vim.wo.winpinned
+
 --- Minimal number of columns for the current window.  This is not a hard
 --- minimum, Vim will use fewer columns if there is not enough room.  If
 --- the current window is smaller, its size is increased, at the cost of