Add _detect_matching_structure(): detection based on control flow
pattern, not variable naming conventions. Uses 5 structural signals:
1. READ + AT END + EOF pattern
2. PERFORM UNTIL with EOF condition
3. ELSE body with conditional READ (matching core)
4. IF comparing hyphenated fields (cross-file comparison)
5. Multi-file OPEN INPUT
5/5 signals → 0.55, 4/5 → 0.50, 3/5 → 0.40.
Real-world impact: matching programs with key fields named CUST-CODE
and ORDR-CODE (no '-KEY' in name) are now correctly detected.
Also:
- Rule engine type priority: main types (マッチング etc.) override
secondary types (M:N, DIVIDE) when keyword confidence is low
- has_structural_match injected into features so rule engine can use it
- matching_vs_keybreak accepts equality IFs as matching evidence
- New test: test_structural_matching_no_keyword()
Regression: 764 passed (0 new failures).
NB-076
da5d1058e7