chore: verify stream-json handles 50K tool result threshold (#162)

Add explicit tests documenting that the parser gracefully handles both
large inline tool results (>50K chars) and null content from persisted
results introduced in Claude CLI v2.1.51.

src-tauri/src/wsl_bridge.rs

@@ -2412,4 +2412,29 @@ mod tests {
         let content = serde_json::json!([]);
         assert_eq!(extract_tool_result_text(&content), None);
     }
+
+    // Verify the 50K tool result persistence threshold (CLI v2.1.51+).
+    // Results > 50K chars are now persisted to disk; the stream may send null
+    // or a large inline string. Both must be handled without panicking.
+    #[test]
+    fn test_extract_tool_result_text_large_content_above_50k_threshold() {
+        let large_text = "x".repeat(60_000);
+        let content = serde_json::Value::String(large_text.clone());
+        assert_eq!(extract_tool_result_text(&content), Some(large_text));
+    }
+
+    #[test]
+    fn test_tool_result_deserializes_with_null_content() {
+        let json = r#"{"type":"tool_result","tool_use_id":"toolu_abc","content":null}"#;
+        let block: ContentBlock = serde_json::from_str(json).unwrap();
+        if let ContentBlock::ToolResult { tool_use_id, content, is_error } = block {
+            assert_eq!(tool_use_id, "toolu_abc");
+            assert!(content.is_null());
+            assert_eq!(is_error, None);
+            // Persisted-to-disk results produce null content → no preview shown
+            assert_eq!(extract_tool_result_text(&content), None);
+        } else {
+            panic!("Expected ToolResult variant");
+        }
+    }
 }