test(data): allow cold imports in tokenizer fork safety check

The outer 30-second subprocess timeout includes Bridge model registration imports. A fresh local run spent 33.66 seconds importing and completed forked tokenization by 33.78 seconds. Use the existing 180-second import-test budget while preserving the 10-second result.get timeout that detects tokenizer deadlocks.

Validation: all 41 GPT SFT dataset tests passed with the pinned MCore dataset helper built in a temporary container copy; pre-commit --all-files passed; independent diff review found no issues.
Signed-off-by: Chen Cui <chcui@nvidia.com>

Author: cuichenx

tests/unit_tests/data/datasets/test_gpt_sft.py

@@ -148,7 +148,9 @@ def encode_batch():
         capture_output=True,
         env=environment,
         text=True,
-        timeout=30,
+        # A fresh Bridge import loads all model registrations and can exceed 30s
+        # on CI. Keep the actual forked tokenization bounded by result.get(10s).
+        timeout=180,
         check=False,
     )
     assert result.returncode == 0, result.stderr