test: add unit test for backslash path normalization in blast radius

Directly tests format_blast_radius_summary with Windows-style backslash
paths to verify they are normalized to forward slashes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: haasonsaas

src/review/pipeline/postprocess/blast_radius.rs

@@ -140,6 +140,35 @@ mod tests {
         assert!(comments[0].tags.iter().any(|tag| tag == "blast-radius:3"));
     }
 
+    #[test]
+    fn format_blast_radius_summary_normalizes_backslash_paths() {
+        use super::format_blast_radius_summary;
+
+        let dependents = vec![
+            PathBuf::from("src\\a.rs"),
+            PathBuf::from("src\\b.rs"),
+            PathBuf::from("src\\c.rs"),
+        ];
+
+        let summary = format_blast_radius_summary(&dependents);
+        assert!(
+            summary.contains("src/a.rs"),
+            "expected forward slashes in summary, got: {summary}"
+        );
+        assert!(
+            summary.contains("src/b.rs"),
+            "expected forward slashes in summary, got: {summary}"
+        );
+        assert!(
+            summary.contains("src/c.rs"),
+            "expected forward slashes in summary, got: {summary}"
+        );
+        assert!(
+            !summary.contains('\\'),
+            "summary should not contain backslashes: {summary}"
+        );
+    }
+
     #[test]
     fn skips_blast_radius_summary_below_threshold() {
         let dir = tempfile::tempdir().unwrap();