修复: 协议层与体验缺陷六件

- temperature 按模型适配,仅收 1 的模型不再 400
- 流式 error 帧不再被 choices 必填整帧丢弃
- 只读缓存写后失效
- git diff 中文截断撞 UTF-8 边界 panic
- 非视觉模型纯图片直接拒绝
- 全局快捷键补输入焦点守卫

src-tauri/src/commands/ai/tools/git.rs

@@ -156,9 +156,13 @@ async fn run_git_diff(working_dir: &str, staged: bool) -> serde_json::Value {
     let mut patch_args = vec!["diff"];
     if staged { patch_args.push("--cached"); }
     let patch_raw = exec_git_exit(working_dir, &patch_args).await.0;
-    // 截断到 8000 字符(防大体量 diff)
+    // 截断到 8000 字符(防大体量 diff);中文字节切片撞 UTF-8 边界会 panic,回退到字符边界
     let patch_truncated = if patch_raw.len() > 8000 {
-        format!("{}\n... (diff 截断,共 {} 字符)", &patch_raw[..8000], patch_raw.len())
+        let mut end = 8000;
+        while !patch_raw.is_char_boundary(end) {
+            end -= 1;
+        }
+        format!("{}\n... (diff 截断,共 {} 字符)", &patch_raw[..end], patch_raw.len())
     } else {
         patch_raw
     };