refactor(harness): route workflow persistence through repositories

harness/tht/taskdoc.py

@@ -15,6 +15,7 @@ from dataclasses import dataclass
 from pathlib import Path
 
 from tht.phase import effective_decisions
+from tht.session.models import SessionSnapshot
 from tht.workflow import load_workflow
 
 MAX_BODY_BYTES = 80_000  # ~20k token (target per task document di una fase)
@@ -50,7 +51,7 @@ def _slice_schema_linking(raw: str, promoted_tables: list[str] | None) -> str:
 
 
 def generate_task_doc(
-    session_dir: Path | str,
+    session_dir: Path | str | SessionSnapshot,
     phase: int,
     promoted_tables: list[str] | None = None,
 ) -> TaskDoc:
@@ -62,20 +63,21 @@ def generate_task_doc(
     - Brief delle decisioni effective (esclude stale post-rollback, esclude ritirate).
     - Header del task con il numero/nome della fase.
     """
-    session_dir = Path(session_dir)
+    snapshot = session_dir if isinstance(session_dir, SessionSnapshot) else None
+    session_dir = None if snapshot is not None else Path(session_dir)
     parts: list[str] = []
 
-    q = session_dir / "question.md"
-    if q.exists():
-        parts.append("## Domanda\n" + q.read_text())
+    question = snapshot.artifacts.get("question") if snapshot else (session_dir / "question.md").read_text() if (session_dir / "question.md").exists() else None
+    if question:
+        parts.append("## Domanda\n" + question)
 
-    sl = session_dir / "schema_linking.json"
-    if sl.exists() and phase >= 4:
-        sliced = _slice_schema_linking(sl.read_text(), promoted_tables)
+    linking = snapshot.artifacts.get("schema_linking") if snapshot else (session_dir / "schema_linking.json").read_text() if (session_dir / "schema_linking.json").exists() else None
+    if linking and phase >= 4:
+        sliced = _slice_schema_linking(linking, promoted_tables)
         parts.append("## Schema linking (deciso)\n```json\n" + sliced + "\n```")
 
     # Brief decisioni effective (D15-aware)
-    eff = effective_decisions(session_dir)
+    eff = effective_decisions(snapshot or session_dir)
     if eff:
         lines = [f"- {d.type} | {d.subject} | {d.detail}" for d in eff]
         parts.append("## Decisioni effettive (effective)\n" + "\n".join(lines))