test: add L1 data generation + L2 classifier validation (58 tests)

Phase C-D complete:
- test_l1_data_generation.py — 8 tests verifying generate_data across all P0 groups
- test_l2_classifier.py — 16 existing + 34 P0 classification verification tests
- hina/pipeline/__init__.py — export classify_program for cleaner imports

Key findings:
- Classifier correctly detects: CALL→子程序调用, CICS→online,
  DB→DB操作, ORGANIZATION IS→文件编成, DIVIDE→DIVIDE_50.0,
  ASCII/EBCDIC→编码转换 (keyword match)
- Rule engine provides baseline 項目チェック(重複含まず) for programs
  without L1 keyword matches
- SD keyword (SORT/MERGE sort-file) breaks Lark parser (known limitation)
- Full regression: 749 passed (0 new failures)

hina/pipeline/__init__.py

@@ -1 +1,5 @@
 """HINA 完整类型判定管道。"""
+
+from .pipeline import classify_program
+
+__all__ = ["classify_program"]