Revert "refactor: message content (#1424)" (#1442)

This reverts commit ae8497faf1.

lua/avante/path.lua

@@ -5,6 +5,18 @@ local Path = require("plenary.path")
 local Scan = require("plenary.scandir")
 local Config = require("avante.config")
 
+---@class avante.ChatHistoryEntry
+---@field timestamp string
+---@field provider string
+---@field model string
+---@field request string
+---@field response string
+---@field original_response string
+---@field selected_file {filepath: string}?
+---@field selected_code {filetype: string, content: string}?
+---@field reset_memory boolean?
+---@field selected_filepaths string[] | nil
+
 ---@class avante.Path
 ---@field history_path Path
 ---@field cache_path Path