feat(l1): start_ai_build_session

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/tests/test_l1_session_service.py

@@ -778,6 +778,24 @@ async def test_escalate_without_walk_reason_is_optional(test_db: AsyncSession):
     assert session.escalation_reason_category == "no_kb_content"
 
 
+# ---------------------------------------------------------------------------
+# T7: start_ai_build_session
+# ---------------------------------------------------------------------------
+
+@pytest.mark.asyncio
+async def test_start_ai_build_session(test_db: AsyncSession):
+    from app.services import l1_session_service as svc
+    account = await _make_account(test_db)
+    l1_user = await _make_user(test_db, account_id=account.id)
+    s = await svc.start_ai_build_session(
+        test_db, account_id=account.id, user=l1_user,
+        ticket_id="t-ai", ticket_kind="internal",
+    )
+    assert s.session_kind == "ai_build"
+    assert s.flow_id is None and s.flow_proposal_id is None
+    assert s.status == "active"
+
+
 # ---------------------------------------------------------------------------
 # T14 audit log tests (spec §5.6.1)
 # ---------------------------------------------------------------------------