docs: Clarify FailureInfo write methods include rule columns (#219)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: borchero <22455425+borchero@users.noreply.github.com>

Author: Copilot

dataframely/filter_result.py

@@ -143,7 +143,11 @@ def __len__(self) -> int:
     # ---------------------------------- PERSISTENCE --------------------------------- #
 
     def write_parquet(self, file: str | Path | IO[bytes], **kwargs: Any) -> None:
-        """Write the failure info to a parquet file.
+        """Write the failure info to a single parquet file.
+
+        Writes the invalid rows along with additional boolean rule columns indicating
+        which validation rules failed. Unlike :meth:`invalid`, this includes columns
+        for each rule, where ``False`` indicates the rule failed for that row.
 
         Args:
             file: The file path or writable file-like object to which to write the
@@ -162,7 +166,11 @@ def write_parquet(self, file: str | Path | IO[bytes], **kwargs: Any) -> None:
     def sink_parquet(
         self, file: str | Path | IO[bytes] | PartitioningScheme, **kwargs: Any
     ) -> None:
-        """Stream the failure info to a parquet file.
+        """Stream the failure info to a single parquet file.
+
+        Writes the invalid rows along with additional boolean rule columns indicating
+        which validation rules failed. Unlike :meth:`invalid`, this includes columns
+        for each rule, where ``False`` indicates the rule failed for that row.
 
         Args:
             file: The file path or writable file-like object to which to write the
@@ -234,6 +242,10 @@ def write_delta(
     ) -> None:
         """Write the failure info to a delta lake table.
 
+        Writes the invalid rows along with additional boolean rule columns indicating
+        which validation rules failed. Unlike :meth:`invalid`, this includes columns
+        for each rule, where ``False`` indicates the rule failed for that row.
+
         Args:
             target: The file path or DeltaTable to which to write the delta lake data.
             kwargs: Additional keyword arguments passed directly to