refactor(src): migrate src/log_registry.py to Result[T] error handling (2 sites)

Migrates the 2 try/except sites in LogRegistry:

1. save_registry() - line 132: was except Exception: print(...)
   Now except OSError: and returns Result[bool] with ErrorInfo on
   failure. Removed the print() diagnostic.

2. update_auto_whitelist_status() - line 246: was except Exception: pass
   Now except OSError: (narrowed). No return value change since
   the method returns None anyway.

Both sites narrowed from broad except Exception to specific stdlib
I/O exceptions. Callers of save_registry() (register_session,
update_session_metadata) ignore the Result return value.

Tests verified:
- tests/test_log_registry.py (5 tests) PASS
- tests/test_logging_e2e.py (1 test) PASS
- tests/test_auto_whitelist.py (4 tests) PASS

src/log_registry.py

@@ -46,6 +46,8 @@ import tomllib
 from datetime import datetime
 from typing   import Any
 
+from src.result_types import Result, ErrorInfo, ErrorKind
+
 
 class LogRegistry:
  """
@@ -98,7 +100,7 @@ class LogRegistry:
   else:
    self.data = {}
 
- def save_registry(self) -> None:
+ def save_registry(self) -> Result[bool]:
   """
   Serializes and saves the current registry data to the TOML file.
   Converts internal datetime objects to ISO format strings for compatibility.
@@ -129,8 +131,9 @@ class LogRegistry:
     data_to_save[session_id] = session_data_copy
    with open(self.registry_path, 'wb') as f:
     tomli_w.dump(data_to_save, f)
-  except Exception as e:
-   print(f"Error saving registry to {self.registry_path}: {e}")
+   return Result(data=True)
+  except OSError as e:
+   return Result(data=False, errors=[ErrorInfo(kind=ErrorKind.INTERNAL, message=str(e), source="log_registry.save_registry", original=e)])
 
  def register_session(self, session_id: str, path: str, start_time: datetime | str) -> None:
   """
@@ -241,9 +244,9 @@ class LogRegistry:
          for kw in keywords_to_check:
           if kw in line and kw not in found_keywords:
            found_keywords.append(kw)
-      except Exception:
+      except OSError:
        pass
-  except Exception:
+  except OSError:
    pass
   size_kb     = total_size_bytes / 1024
   whitelisted = False