fix(workflow): avoid redundant file I/O when resolving callsite source

Previously, the `Atom` class attempted to reread the source file to retrieve
callsite source code during runtime error reporting. This fallback logic is now
commented out to prevent repeated file reads, which can be inefficient and
unnecessary.

A `TODO` comment has been added to centralize line buffer access in the
service layer. In the meantime, if `callsite_source` is missing, it will simply
be omitted rather than triggering another file read.

Also updated `register_error(...)` to explicitly include the `source` field,
defaulting to an empty string when unavailable.

Author: BloggerBust

preswald/interfaces/workflow.py

@@ -176,21 +176,27 @@ def wrapped_func(*args, **kwargs):
 
                 # if callsite source was not provided, attempt to
                 # capture this info where the atom was defined
-                if not callsite_source and callsite_filename:
-                    try:
-                        with open(callsite_filename, 'r') as f:
-                            lines = f.readlines()
-                            lineno = callsite_lineno or 0
-                            callsite_source = lines[lineno - 1].strip() if 0 < lineno <= len(lines) else ""
-                            self.callsite_metadata['callsite_source'] = callsite_source
-
-                    except Exception:
-                        pass
+                #
+                # TODO(preswald): Centralize source line buffering per filename in the service layer.
+                # This would allow both the AST transformer and Atom class to fetch source snippets
+                # without reopening the file. Until then, skip this fallback to avoid redundant I/O.
+                #
+                # if not callsite_source and callsite_filename:
+                #     try:
+                #         with open(callsite_filename, 'r') as f:
+                #             lines = f.readlines()
+                #             lineno = callsite_lineno or 0
+                #             callsite_source = lines[lineno - 1].strip() if 0 < lineno <= len(lines) else ""
+                #             self.callsite_metadata['callsite_source'] = callsite_source
+
+                #     except Exception:
+                #         pass
 
                 register_error(
                     type="runtime",
                     filename=callsite_filename or "<unknown>",
                     lineno=callsite_lineno or 0,
+                    source=callsite_source or "",
                     message=str(e),
                     atom_name=self.name,
                 )