Load the config before viewing a prompt

Lazy-load the Neural config before viewing a prompt, and update tests
to reset state better.

autoload/neural.vim

@@ -294,6 +294,9 @@ endfunction
 
 " Print the prompt that Neural will use in full.
 function! neural#ViewPrompt(...) abort
+    " Reload the Neural config on a prompt request if needed.
+    call neural#config#Load()
+
     " Take the first argument or nothing.
     let l:prompt = get(a:000, 0, '')
     let l:buffer = bufnr('')

test/vim/test_buffer.vader

@@ -11,8 +11,11 @@ Before:
     call add(g:calls, ['neural#Run', a:prompt, a:options])
   endfunction
 
+  let g:output = ''
+
 After:
   unlet! g:calls
+  unlet! g:output
 
   runtime autoload/neural/job.vim
 

test/vim/test_view_prompt.vader

@@ -1,4 +1,12 @@
+Before:
+  Save g:neural
+
+  unlet! g:neural
+  let g:output = ''
+
 After:
+  Restore
+
   unlet! g:output
 
 Given markdown(An empty Markdown file):