feat: matching program subtype discrimination (1:1/1:N/M:N/MxN)

Add _resolve_matching_subtype post-processing step in classify_program()
that distinguishes matching program subtypes based on key variable naming
patterns and file/structural features:

Rules (in priority order):
1. 二段階 → 二段階 (already handled by rule engine)
2. 3 files + WS-SAVE-KEY → M:N→MxN (MT20)
3. WS-PREV-KEY present → 混合 (already handled, MT32)
4. WS-MAST-KEY + WS-TRAN-KEY → 1:N (MT02)
5. >=3 KEY vars + >=2 files → M:N (MT33)
6. Otherwise → 1:1 (MT01, MT03, MT18, MT19)

Results:
  MT01→1:1, MT02→1:N, MT03→1:1, MT16/17→二段階,
  MT18/19→1:1, MT20→M:N→MxN, MT33→M:N

Also fix double-backslash regex bug in classifier.py and pipeline.py
(r'[-\w]' should be r'[\w-]' for word character class).
Regression: 745 passed (unchanged).

hina/classifier.py

@@ -23,7 +23,7 @@ L1_RULES: list[tuple[str, list[str], float]] = [
     ("编辑输出", ["WRITE AFTER", "WRITE BEFORE"], 0.80),
     ("文件编成", ["ORGANIZATION IS"], 0.99),
     ("替代索引", ["ALTERNATE RECORD KEY"], 0.99),
-    ("マッチング", ["re:WS-[-\\w]*KEY"], 0.65),
+    ("マッチング", ["re:WS-[\\w-]*KEY"], 0.65),
 ]
 
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