feat: center help box, auto-dismiss after 2s, bold help hint

lua/tiny-debugger/help.lua

@@ -4,6 +4,7 @@ local M = {}
 
 local win_id = nil
 local buf_id = nil
+local timer = nil
 
 local modal_info = {
   { "continue", "Continue" },
@@ -16,7 +17,6 @@ local modal_info = {
   { "eval", "Eval in REPL" },
   { "terminate", "Quit debugging" },
   { "restart", "Restart session" },
-  { "help", "Show this help" },
 }
 
 local global_info = {
@@ -49,11 +49,21 @@ local function build_content()
     if key then add(key, pair[2]) end
   end
 
+  -- highlight line at the bottom
+  local help_key = config.opts.keys.help or "?"
   lines[#lines + 1] = ""
+  lines[#lines + 1] = " Press " .. help_key .. " for help"
+  lines[#lines + 1] = ""
+
   return lines, width + 2
 end
 
 function M.close()
+  if timer then
+    timer:stop()
+    timer:close()
+    timer = nil
+  end
   if win_id and vim.api.nvim_win_is_valid(win_id) then
     vim.api.nvim_win_close(win_id, true)
   end
@@ -68,29 +78,39 @@ function M.open()
   M.close()
 
   local lines, width = build_content()
+  local height = #lines
 
   buf_id = vim.api.nvim_create_buf(false, true)
   vim.api.nvim_buf_set_lines(buf_id, 0, -1, false, lines)
+
+  -- highlight the "Press ? for help" line
+  local hl_line = height - 2
+  vim.api.nvim_buf_add_highlight(buf_id, -1, "Bold", hl_line, 0, -1)
+
   vim.bo[buf_id].modifiable = false
   vim.bo[buf_id].bufhidden = "wipe"
 
+  -- center the float
+  local ed_w = vim.o.columns
+  local ed_h = vim.o.lines
+  local row = math.floor((ed_h - height) / 2)
+  local col = math.floor((ed_w - width) / 2)
+
   win_id = vim.api.nvim_open_win(buf_id, false, {
     relative = "editor",
-    anchor = "SE",
-    row = vim.o.lines - 2,
-    col = vim.o.columns,
+    row = row,
+    col = col,
     width = width,
-    height = #lines,
+    height = height,
     style = "minimal",
     border = "rounded",
     focusable = false,
     noautocmd = true,
   })
 
-  vim.api.nvim_create_autocmd({ "CursorMoved", "InsertEnter", "CmdlineEnter" }, {
-    once = true,
-    callback = function() M.close() end,
-  })
+  -- auto-close after 2 seconds
+  timer = vim.uv.new_timer()
+  timer:start(2000, 0, vim.schedule_wrap(function() M.close() end))
 end
 
 function M.is_open()