remove parquet output support

Nate has given up on getting wikiq to output parquet directly because it
makes too many unpredictable large memory allocations. The workflow now
outputs JSONL in a single pass and then uses spark (wikiq_spark) to index
it as parquet in a second pass.

Remove the parquet output path along with the machinery that existed only
to support it: checkpoint files, resume temp-file merging, namespace
partitioning, and file rotation (--partition-namespaces,
--max-revisions-per-file). Resume support remains for JSONL output, where
the resume point is derived from the last complete line of the output
file. Also remove the parquet tests and baseline files.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/wikiq_test_utils.py

@@ -42,17 +42,8 @@ class WikiqTester:
             else:
                 shutil.rmtree(self.output)
 
-        # Also clean up resume-related files
-        for temp_suffix in [".resume_temp", ".checkpoint", ".merged"]:
-            temp_path = self.output + temp_suffix
-            if os.path.exists(temp_path):
-                if os.path.isfile(temp_path):
-                    os.remove(temp_path)
-                else:
-                    shutil.rmtree(temp_path)
-
-        # For JSONL and Parquet, self.output is a file path. Create parent directory if needed.
-        if out_format in ("jsonl", "parquet"):
+        # For JSONL, self.output is a file path. Create parent directory if needed.
+        if out_format == "jsonl":
             parent_dir = os.path.dirname(self.output)
             if parent_dir:
                 os.makedirs(parent_dir, exist_ok=True)