R13: final sweep — EXEC stripping + INSPECT bugfix + more EQ assertions

1. Lark: preprocess strips EXEC CICS/SQL...END-EXEC blocks
   -> CI01_CICS/DB01_SELECT_UPDATE now parse, 75/75 samples pass
2. propagate_assignments INSPECT TALLYING bugfix:
   was reading source from count_var (wrong field) instead of
   asgn['tgt']. Now CNT='005' instead of '003' for len(HELLO)=5.
3. 26 new EQ/falsifiable assertions added (propagate chains,
   orchestrator state, data_writer, report generator)
4. Hardened: ACCEPT DATE string len check, DataWriter JSON format

16 suites / 0 FAIL.

Co-Authored-By: Claude <noreply@anthropic.com>

cobol_testgen/core.py

@@ -1417,7 +1417,9 @@ def propagate_assignments(rec, assignments, fields, file_sec=None):
             resolved_tgt = _resolve_subscript(tgt, rec)
             if resolved_tgt not in rec:
                 continue
-            src_val = str(rec[resolved_tgt])
+            inspect_src = asgn.get('tgt', tgt)
+            resolved_src = _resolve_subscript(inspect_src, rec)
+            src_val = str(rec.get(resolved_src, ''))
             for op_type, params in asgn.get('sub_ops', []):
                 if op_type == 'tally':
                     cv = params['count_var'].upper()