fix: namespace ops must happen on main loop

this plugin is becoming a bit of vim.schedule hell...
maybe the :and_then() callback should make sure it runs on the main
loop? maybe offer an :and_then(), which runs on main loop, and a :and_then_soon(),
which runs in the callback thread itself

lua/codemp/workspace.lua

@@ -155,6 +155,7 @@ local function join(workspace)
 		register_cursor_callback(ws:cursor(), ws:id())
 		register_cursor_handler(ws:cursor())
 		CODEMP.workspace = ws
+		vim.schedule(function ()
 			for _, user in pairs(CODEMP.workspace:user_list()) do
 				buffers.users[user.name] = ""
 				user_hl[user.name] = {
@@ -165,12 +166,14 @@ local function join(workspace)
 				}
 			end
 			require('codemp.window').update()
+		end)
 		local async = vim.uv.new_async(function ()
 			while true do
 				local event = ws:try_recv():await()
 				if event == nil then break end
 				if event.type == "UserLeave" then
 					if buffers.users[event.name] ~= nil then
+						vim.schedule(function()
 							local buf_name = buffers.users[event.name]
 							local buf_id = buffers.map_rev[buf_name]
 							if buf_id ~= nil then
@@ -178,8 +181,10 @@ local function join(workspace)
 							end
 							buffers.users[event.name] = nil
 							user_hl[event.name] = nil
+						end)
 					end
 				elseif event.type == "UserJoin" then
+					vim.schedule(function()
 						buffers.users[event.name] = ""
 						user_hl[event.name] = {
 							ns = vim.api.nvim_create_namespace("codemp-cursor-" .. event.name),
@@ -187,6 +192,7 @@ local function join(workspace)
 							pos = { 0, 0 },
 							mark = nil,
 						}
+					end)
 				end
 			end
 			vim.schedule(function () require('codemp.window').update() end)