Moving to neovim 0.11, new calc, keys streamlined

Keybindings:

- <space>E (explain error) now is <space>x
- dropped <C-W>0 and following, were remainders from Emacs
- insert: <C-Del> now deletes word right of cursor

LSP:

- diagnostics popup replaced with neovim 0.11 virtual lines (much nicer)

Options:

- neo-tree width dropped, was too wide
- workspaces no longer auto open, was interfering with using neovim as
  git client or file manager

Plugins:

- replaced cmp-rpncalc with qalc.nvim (which uses the qalc cli)

lua/keybindings.lua

@@ -77,12 +77,9 @@ vim.keymap.set('n', '<space>mc', mywords.uhl_all, { desc = "Clear all highlights
 -- Shortcuts which are known from Emacs
 --
 ------------------------------------------
-vim.keymap.set('n', '<C-W>0', ":hide<CR>", { desc = "Win: close current" })
-vim.keymap.set('n', '<C-W>1', ":only<CR>", { desc = "Win: close others" })
-vim.keymap.set('n', '<C-W>2', ":split<CR>", { desc = "Win: split horizontally" })
-vim.keymap.set('n', '<C-W>2', ":vsplit<CR>", { desc = "Win: split vertically" })
 vim.keymap.set('n', '<space>q', "gwap", { desc = "Wrap paragraph" })
 vim.keymap.set('n', '<esc><esc>', ":silent! nohls<CR>", { desc = "Clear search" })
+vim.keymap.set('i', '<c-Del>', '<c-o>dW', {desc = "Delete word right" })
 
 -- horizontally scroll with mouse
 vim.keymap.set('n', '<S-ScrollWheelUp>', 'zh')