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/lsp.lua

@@ -57,7 +57,11 @@ local on_attach = function(client, bufnr)
   local fzf = require('fzf-lua')
   vim.keymap.set('n', '<space>d', fzf.diagnostics_document, { desc = "Document diagnostics" })
   vim.keymap.set('n', '<space>D', fzf.diagnostics_workspace, { desc = "Workspace diagnostics" })
-  vim.keymap.set('n', '<space>e', vim.diagnostic.open_float, { desc = "Popup diagnostics" })
+  -- vim.keymap.set('n', '<space>E', vim.diagnostic.open_float, { desc = "Popup diagnostics" })
+  vim.keymap.set('n', '<space>e', function()
+    local new_config = not vim.diagnostic.config().virtual_lines
+    vim.diagnostic.config({ virtual_lines = new_config })
+  end, { desc = "Virtual line diagnostics" })
   vim.keymap.set('n', '<space>s', fzf.lsp_document_symbols, { desc = "Doc symbols" })
   vim.keymap.set('n', '<space>c', fzf.lsp_code_actions, { desc = "Code Actions" })
   vim.keymap.set('n', '<space>[', vim.diagnostic.goto_prev, { desc = "Previous diagnostics" })