docs: 更新 README feature 表 + 升级指南 + 示例注释 + roadmap 同步

- README 添加 feature 组合表 + 模块级 features 清单 + 升级指南
- 18 个 example 顶部添加 Required features 注释
- roadmap.md 和 roadmap-v0.3.2.md 同步 Phase 26-27 完成状态
- cargo fmt 全量格式化（修复预存格式问题，CI format job 可通过）

src/llm/provider/anthropic.rs

@@ -18,7 +18,6 @@ use serde::{Deserialize, Serialize};
 use serde_json::{Value, json};
 use tracing::{debug, error, info, warn};
 
-use crate::llm::{LlmProvider, ProviderCapabilities, ProviderFeatures};
 use crate::llm::error::LlmError;
 use crate::llm::types::message::{ContentBlock, ContentBlockType, Message};
 use crate::llm::types::request_v2::MessageRequest;
@@ -26,6 +25,7 @@ use crate::llm::types::response_v2::{
     MessageResponse, PartialMessageResponse, PartialUsage, StopReason, StreamEvent,
 };
 use crate::llm::types::usage::Usage;
+use crate::llm::{LlmProvider, ProviderCapabilities, ProviderFeatures};
 
 /// Anthropic Provider 默认 `max_tokens` 兜底值。
 ///

src/llm/provider/ollama.rs

@@ -11,10 +11,10 @@ use futures_core::Stream;
 use reqwest::Client;
 
 use super::openai::GenericOpenaiProvider;
-use crate::llm::{LlmProvider, ProviderCapabilities};
 use crate::llm::error::LlmError;
 use crate::llm::types::request_v2::MessageRequest;
 use crate::llm::types::response_v2::{MessageResponse, StreamEvent};
+use crate::llm::{LlmProvider, ProviderCapabilities};
 
 /// Ollama 本地 Provider —— OpenAI-compatible 协议的 newtype 包装。
 ///

src/llm/provider/openai.rs

@@ -21,7 +21,6 @@ use serde::Serialize;
 use serde_json::Value;
 use tracing::{debug, error, info};
 
-use crate::llm::{LlmProvider, ProviderCapabilities, ProviderFeatures};
 use crate::llm::convert::{from_openai, to_openai};
 use crate::llm::error::LlmError;
 use crate::llm::types::message::{ContentBlock, ContentBlockType, Message};
@@ -32,6 +31,7 @@ use crate::llm::types::response_v2::{
 };
 use crate::llm::types::shared::{FinishReason, ResponseFormat, ServiceTier, StopSequence};
 use crate::llm::types::tool::{OpenaiToolCall, OpenaiToolDefinition, ToolChoice};
+use crate::llm::{LlmProvider, ProviderCapabilities, ProviderFeatures};
 use serde::Deserialize;
 
 // =============================================================================

src/llm/provider/registry.rs

@@ -2,9 +2,9 @@
 
 use std::collections::HashMap;
 
+use crate::llm::LlmProvider;
 use crate::llm::error::LlmError;
 use crate::llm::provider::{ProviderConfig, ProviderType, create_provider};
-use crate::llm::LlmProvider;
 
 /// Provider 注册表 —— 管理多个 LLM Provider 实例。
 ///