fix(health): floating window closes when opening TOC (gO)

fix(health): floating window closes when opening TOC (gO) #34794

Problem: Health check floating window gets closed when pressing 'gO' to show TOC because LSP floating preview system auto-closes on BufEnter events triggered by :lopen.

Solution: Temporarily disable BufEnter event for the current window during TOC operations and adjust window layout to prevent overlap.
(cherry picked from commit 28b7c2df52)

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

test/functional/plugin/health_spec.lua

@@ -68,7 +68,10 @@ describe(':checkhealth', function()
   end)
 
   it('vim.g.health', function()
-    clear()
+    clear {
+      args_rm = { '-u' },
+      args = { '--clean', '+set runtimepath+=test/functional/fixtures' },
+    }
     command("let g:health = {'style':'float'}")
     command('checkhealth lsp')
     eq(
@@ -77,6 +80,14 @@ describe(':checkhealth', function()
       return vim.api.nvim_win_get_config(0).relative
     ]])
     )
+
+    -- gO should not close the :checkhealth floating window. #34784
+    command('checkhealth full_render')
+    local win = api.nvim_get_current_win()
+    api.nvim_win_set_cursor(win, { 5, 1 })
+    n.feed('gO')
+    eq(true, api.nvim_win_is_valid(win))
+    eq('qf', api.nvim_get_option_value('filetype', { buf = 0 }))
   end)
 
   it("vim.provider works with a misconfigured 'shell'", function()