feat: config-driven multi-scenario + gcda accumulation fix + gcov merge fix

Config-driven architecture:
- coverage_dates: YAML-driven date replacement for LEAVE_RECORDS
- row_overrides: per-scenario field overrides (e.g. STATUS='9')
- delete_all_rows: per-scenario table emptying for empty-cursor tests

gcda accumulation fix (V3 bug #7):
- Delete .gcda before each scenario run to prevent GnuCOBOL accumulation
- Force-copy scenario gcda (skip mtime check)
- Copy scenario DB to CWD data/kin.db for CONNECT TO path resolution

Multi-run gcov merge fix:
- Always merge multi-run gcov data regardless of generate_coverage flag
- Fix v3_root UnboundLocalError in cleanup path

Other fixes:
- _make_key_unique: skip WHERE-constrained columns to avoid PK conflict
- incremental_supplement: support fields_dict for base record generation
- check_coverage: use structure coverage data if available
- orchestrator.py: filter _-prefixed fields in TestCase; merge Agent2Data cases

config/program_schema.py

@@ -40,6 +40,8 @@ class ScenarioDef:
     id: str
     sysin: SysinDef = field(default_factory=SysinDef)
     inject_duplicate_pk: bool = False
+    row_overrides: dict[str, dict[str, str]] = field(default_factory=dict)
+    delete_all_rows: bool = False
 
 
 @dataclass
@@ -50,6 +52,7 @@ class ProgramSchema:
     db_type: str = "SQLite"
     db_name: str = "OVERTIME.DB"
     runs: list[ScenarioDef] = field(default_factory=list)
+    coverage_dates: dict[str, list[dict[str, str]]] = field(default_factory=dict)
 
     @classmethod
     def from_yaml(cls, path: str | Path) -> ProgramSchema:
@@ -71,6 +74,8 @@ class ProgramSchema:
                 id=r["id"],
                 sysin=SysinDef(**sysin_raw),
                 inject_duplicate_pk=r.get("inject_duplicate_pk", False),
+                row_overrides=r.get("row_overrides", {}),
+                delete_all_rows=r.get("delete_all_rows", False),
             ))
         return cls(
             program_id=raw["program_id"],
@@ -79,6 +84,7 @@ class ProgramSchema:
             db_type=raw.get("db_type", "SQLite"),
             db_name=raw.get("db_name", "OVERTIME.DB"),
             runs=runs,
+            coverage_dates=raw.get("coverage_dates", {}),
         )