feat(submit): require explicit confirmation for all prepare_submit_job params

Remove defaults from queue, executor_memory, executor_cores,
num_executors, and app_name in prepare_submit_job. All must now be
explicitly confirmed by the caller.

Also add extra_args to the PendingSubmission snapshot so users can
confirm non-conf spark-submit flags (e.g. --jars, --py-files) at
prepare time; confirm_submit_job passes them through to
build_spark_submit_command.

This is an intentional breaking change to the MCP tool contract:
callers can no longer rely on implicit defaults.

tests/unit/test_logging.py

@@ -47,7 +47,15 @@ def test_prepare_submit_job_emits_debug_and_info(log_capture, tmp_path):
     script = tmp_path / "demo.py"
     script.write_text("print('hi')\n")
     log_capture.truncate(0); log_capture.seek(0)
-    submit.prepare_submit_job(connection="prod", script_path=str(script), queue="research")
+    submit.prepare_submit_job(
+        connection="prod",
+        script_path=str(script),
+        queue="research",
+        executor_memory="4G",
+        executor_cores=2,
+        num_executors=2,
+        app_name="test-app",
+    )
     text = log_capture.getvalue()
     assert "DEBUG|prepare_submit_job enter" in text
     assert "INFO|prepare_submit_job ok" in text