重构: DRY截断正典改名收尾

- audit/utils.rs truncate_chars→truncate_chars_ellipsis 正典改名(补…语义),re-export 链同步
- record.rs/generate_image.rs/knowledge_inject.rs/tools/knowledge.rs 调用点全链更新
- df-ai context_helpers.rs 私有版跨 crate 不引依赖保留原名,加正典标注注释
- DRY #11 收口,同名不同义陷阱消除

src-tauri/src/commands/ai/knowledge_inject.rs

@@ -21,7 +21,7 @@ use df_types::types::new_id;
 
 use crate::state::{AppState, ExtractTrigger, LlmConcurrency, log_slow_lock};
 
-use crate::commands::ai::audit::truncate_chars;
+use crate::commands::ai::audit::truncate_chars_ellipsis;
 use crate::commands::err_str;
 
 use super::{AiSession};
@@ -562,7 +562,7 @@ pub(crate) async fn build_knowledge_context(
         let kind = r.kind.clone();
         let title = r.title.clone();
         // 截断 content 防膨胀(注入侧最多 500 字符;走 audit 正典,截断时尾部补 … 提示有省略)
-        let snippet: String = truncate_chars(&r.content, 500);
+        let snippet: String = truncate_chars_ellipsis(&r.content, 500);
         out.push_str(&format!("- [{}] {}: {} (复用 {} 次)\n", kind, title, snippet, r.reuse_count));
     }
     out