feat: floating input (#721)

* feat: add floating input to ask method

Open a floating input similar to the "edit" input for the "ask" input.
Enabled in config via `Config.windows.ask.floating` or by passing
`{ floating = true }` to the `api.ask` method.

Includes logic to ensure the sidebar uses the correct buffer and selection
if an existing sidebar is open for another code buffer.

Also refactored the `selection` module to extract the floating input
logic into a new `PromptInput` class.

* docs: update config options

* feat: more accurate annotations to prevent user misunderstandings

---------

Co-authored-by: yetone <yetoneful@gmail.com>

lua/avante/init.lua

@@ -357,6 +357,27 @@ M.toggle_sidebar = function(opts)
   return sidebar:toggle(opts)
 end
 
+M.is_sidebar_open = function()
+  local sidebar = M.get()
+  if not sidebar then return false end
+  return sidebar:is_open()
+end
+
+---@param opts? AskOptions
+M.open_sidebar = function(opts)
+  opts = opts or {}
+  if opts.ask == nil then opts.ask = true end
+  local sidebar = M.get()
+  if not sidebar then M._init(api.nvim_get_current_tabpage()) end
+  M.current.sidebar:open(opts)
+end
+
+M.close_sidebar = function()
+  local sidebar = M.get()
+  if not sidebar then return end
+  sidebar:close()
+end
+
 M.toggle.debug = H.api(Utils.toggle_wrap({
   name = "debug",
   get = function() return Config.debug end,