refactor: improve avante.nvim configuration with better environment variable handling and documentation

- Replace DEEPSEEK_API_KEY check with THIRD_PARTY_AI_ASSISTANT for more flexible AI integration
- Add comprehensive code comments and documentation for better maintainability
- Improve configuration structure and readability

lua/plugins/avante-nvim.lua

@@ -1,25 +1,48 @@
-if not os.getenv "DEEPSEEK_API_KEY" then return {} end
+-- Configuration module for avante.nvim plugin with DeepSeek API support
+-- Returns configuration only if THIRD_PARTY_AI_ASSISTANT environment variable is set
 
+-- Check for the required environment variable containing the API key
+-- If the key is not set, returns an empty table and the plugin won't load
+local ai_enabled = os.getenv "THIRD_PARTY_AI_ASSISTANT"
+if not ai_enabled or ai_enabled:lower() ~= "true" then return {} end
+
+-- Main plugin configuration object
+---@type LazyPluginSpec[]
 return {
-  { -- further customize the options set by the community
+  {
+    -- Plugin identifier in GitHub repository
     "yetone/avante.nvim",
+    -- Plugin version for compatibility assurance
     version = "0.0.27",
-    ---@type avante.Config
+    -- Plugin configuration options
+    -- Remove the type annotation if avante.Config is undefined
     opts = {
+      -- Primary AI provider for code generation
       provider = "deepseek",
+      -- Provider for automatic code suggestions (autocompletion)
       auto_suggestions_provider = "deepseek",
+      -- Plugin operation mode (commented out, uses default value)
       -- mode = "legacy",
+      -- Plugin behavior settings (commented out)
       -- behaviour = {
       --   auto_apply_diff_after_generation = false,
       --   auto_focus_on_diff_view = true,
       -- },
+      -- AI providers configuration
       providers = {
+        -- Specific configuration for DeepSeek provider
         deepseek = {
+          -- Inheritance of base configuration from OpenAI provider
           __inherited_from = "openai",
+          -- Environment variable name containing the API key
           api_key_name = "DEEPSEEK_API_KEY",
+          -- API endpoint for DeepSeek requests
           endpoint = "https://api.deepseek.com",
+          -- AI model to use (specialized for programming)
           model = "deepseek-coder",
+          -- Maximum number of tokens in model response
           max_tokens = 8192,
+          -- Tools disable flag (commented out)
           -- disable_tools = true,
         },
       },