新增: Phase2 阶段收尾（Sprint 1-20）

重构：删 5 零引用 crate（df-evolve/plugin/stages/task/traceability）+ 清死模块、ai.rs 拆 11 子 module、ai.ts 拆 6 composable、i18n 拆目录
功能：知识库全栈（df-project/scan + CRUD + 时间线 + 前端）、Settings 拆分、appSettings KV 迁移、模型池、LLM 并发 Semaphore
修复：审批持久化根治、ConditionEngine 默认拒绝、NodeRegistry unimplemented 清除、promote 补偿删除、工具结果截断 50KB、路径校验防 symlink 逃逸
文档：B-03 人工审批设计、决策记录三分档、规格契约自检、经验记录、todo 看板、PROGRESS 更新

详见 PROGRESS.md。src-tauri/儿童每日打卡应用/ 与本项目无关，已排除。

crates/df-ai/src/provider.rs

@@ -45,23 +45,26 @@ pub struct ChatMessage {
     /// AI 发起的工具调用列表（role=Assistant 时可能有）
     #[serde(skip_serializing_if = "Option::is_none")]
     pub tool_calls: Option<Vec<ToolCall>>,
+    /// 生成该消息的 model（仅 assistant 消息有，消息级 model 追溯）
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub model: Option<String>,
 }
 
 impl ChatMessage {
     pub fn system(content: impl Into<String>) -> Self {
-        Self { role: MessageRole::System, content: content.into(), tool_call_id: None, tool_calls: None }
+        Self { role: MessageRole::System, content: content.into(), tool_call_id: None, tool_calls: None, model: None }
     }
     pub fn user(content: impl Into<String>) -> Self {
-        Self { role: MessageRole::User, content: content.into(), tool_call_id: None, tool_calls: None }
+        Self { role: MessageRole::User, content: content.into(), tool_call_id: None, tool_calls: None, model: None }
     }
     pub fn assistant(content: impl Into<String>) -> Self {
-        Self { role: MessageRole::Assistant, content: content.into(), tool_call_id: None, tool_calls: None }
+        Self { role: MessageRole::Assistant, content: content.into(), tool_call_id: None, tool_calls: None, model: None }
     }
     pub fn assistant_with_tools(content: impl Into<String>, tool_calls: Vec<ToolCall>) -> Self {
-        Self { role: MessageRole::Assistant, content: content.into(), tool_call_id: None, tool_calls: Some(tool_calls) }
+        Self { role: MessageRole::Assistant, content: content.into(), tool_call_id: None, tool_calls: Some(tool_calls), model: None }
     }
     pub fn tool_result(call_id: impl Into<String>, content: impl Into<String>) -> Self {
-        Self { role: MessageRole::Tool, content: content.into(), tool_call_id: Some(call_id.into()), tool_calls: None }
+        Self { role: MessageRole::Tool, content: content.into(), tool_call_id: Some(call_id.into()), tool_calls: None, model: None }
     }
 }
 
@@ -141,7 +144,7 @@ pub struct CompletionResponse {
 }
 
 /// Token 用量
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
 pub struct TokenUsage {
     pub prompt_tokens: u32,
     pub completion_tokens: u32,
@@ -166,6 +169,9 @@ pub struct StreamChunk {
     /// 工具调用增量（如有）
     #[serde(skip_serializing_if = "Option::is_none")]
     pub tool_calls: Option<Vec<ToolCallDelta>>,
+    /// Token 用量（流末 chunk 携带，由 provider 解析自 SSE usage 事件）
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub usage: Option<TokenUsage>,
 }
 
 /// 工具调用增量（流式中的片段）
@@ -199,6 +205,14 @@ pub trait LlmProvider: Send + Sync {
         request: CompletionRequest,
     ) -> anyhow::Result<StreamResult>;
 
+    /// 文本嵌入：批量文本 → 语义向量(供知识库向量检索)
+    ///
+    /// 默认实现返回 Err(协议不支持)。OpenAI 兼容协议覆盖实现(/v1/embeddings);
+    /// Anthropic 无 embedding API,保持默认。
+    async fn embed(&self, _model: &str, _texts: Vec<String>) -> anyhow::Result<Vec<Vec<f32>>> {
+        anyhow::bail!("该 Provider 不支持 embedding({})", self.name())
+    }
+
     /// Provider 名称
     fn name(&self) -> &str;