fix: improve read_file not-found error with actionable hint (#887)

tools/file_operations.py

@@ -601,8 +601,12 @@ class ShellFileOperations(FileOperations):
         scored.sort(key=lambda x: -x[0])
         similar = [fp for _, fp in scored[:5]]
 
+        hint = " Use search_files to find the correct path before reading."
+        similar_hint = ""
+        if similar:
+            similar_hint = f" Did you mean one of: {', '.join(similar[:3])}?"
         return ReadResult(
-            error=f"File not found: {path}",
+            error=f"File not found: {path}.{similar_hint}{hint}",
             similar_files=similar
         )