feat(l1): l1_session_service resolve / escalate / escalate_without_walk

resolve: sets status=resolved, helpful, resolution_notes, resolved_at;
flips FlowProposal.validated_by_outcome on helpful=True proposal walks;
closes linked internal ticket. PSA close is a Phase 2 stub.

escalate: marks session + internal ticket as escalated. PSA reassign
deferred to Phase 2.

escalate_without_walk: creates an immediately-escalated adhoc session
with no walked_path, used by the BuildAbortedNoKB → Escalate path.

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

backend/app/services/l1_session_service.py

@@ -9,8 +9,10 @@ from uuid import UUID
 
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from app.models.flow_proposal import FlowProposal
 from app.models.l1_walk_session import L1WalkSession
 from app.models.user import User
+from app.services import internal_ticket_service
 
 
 def _resolve_acting_as(user: User) -> Optional[str]:
@@ -149,3 +151,126 @@ async def update_notes(
     session.last_step_at = datetime.now(timezone.utc)
     await db.flush()
     return session
+
+
+async def resolve(
+    db: AsyncSession,
+    *,
+    session_id: UUID,
+    helpful: bool,
+    resolution_notes: str,
+) -> L1WalkSession:
+    """Close a session as resolved.
+
+    - Sets status='resolved', helpful, resolution_notes, resolved_at.
+    - On helpful=True AND session_kind='proposal': flips
+      flow_proposal.validated_by_outcome=True (one-bit aggregate signal).
+    - Closes the linked internal ticket (PSA close stubbed for Phase 2).
+    - Raises ValueError on missing or non-active session.
+    """
+    session = await db.get(L1WalkSession, session_id)
+    if not session:
+        raise ValueError(f"L1WalkSession {session_id} not found")
+    if session.status != "active":
+        raise ValueError(f"Session not active (status={session.status})")
+    now = datetime.now(timezone.utc)
+    session.status = "resolved"
+    session.helpful = helpful
+    session.resolution_notes = resolution_notes
+    session.resolved_at = now
+    session.last_step_at = now
+
+    if helpful and session.session_kind == "proposal" and session.flow_proposal_id:
+        proposal = await db.get(FlowProposal, session.flow_proposal_id)
+        if proposal:
+            proposal.validated_by_outcome = True
+
+    if session.ticket_kind == "internal":
+        await internal_ticket_service.update_status(
+            db,
+            ticket_id=UUID(session.ticket_id),
+            status="resolved",
+            resolution_notes=resolution_notes,
+        )
+    # PSA close deferred to Phase 2 — no-op for now
+
+    await db.flush()
+    return session
+
+
+async def escalate(
+    db: AsyncSession,
+    *,
+    session_id: UUID,
+    reason: str,
+    reason_category: str,
+) -> L1WalkSession:
+    """Escalate an active session to engineering.
+
+    - Sets status='escalated', escalation_reason, escalation_reason_category, resolved_at.
+    - Marks the linked internal ticket as escalated (PSA reassign deferred to Phase 2).
+    - Raises ValueError on missing or non-active session.
+    """
+    session = await db.get(L1WalkSession, session_id)
+    if not session:
+        raise ValueError(f"L1WalkSession {session_id} not found")
+    if session.status != "active":
+        raise ValueError(f"Session not active (status={session.status})")
+    now = datetime.now(timezone.utc)
+    session.status = "escalated"
+    session.escalation_reason = reason
+    session.escalation_reason_category = reason_category
+    session.resolved_at = now
+    session.last_step_at = now
+
+    if session.ticket_kind == "internal":
+        await internal_ticket_service.update_status(
+            db,
+            ticket_id=UUID(session.ticket_id),
+            status="escalated",
+        )
+    # PSA reassign deferred to Phase 2
+
+    await db.flush()
+    return session
+
+
+async def escalate_without_walk(
+    db: AsyncSession,
+    *,
+    account_id: UUID,
+    user: User,
+    ticket_id: str,
+    ticket_kind: str,
+    reason_category: str,
+    reason: Optional[str] = None,
+) -> L1WalkSession:
+    """Create an immediately-escalated session with no walked_path.
+
+    Used from the BuildAbortedNoKB screen (no KB content available to walk a
+    tree). Captures the call as an audit record + escalates the ticket without
+    requiring a walker session in between.
+    """
+    now = datetime.now(timezone.utc)
+    session = L1WalkSession(
+        account_id=account_id,
+        created_by_user_id=user.id,
+        acting_as=_resolve_acting_as(user),
+        ticket_id=ticket_id,
+        ticket_kind=ticket_kind,
+        session_kind="adhoc",
+        status="escalated",
+        escalation_reason=reason,
+        escalation_reason_category=reason_category,
+        resolved_at=now,
+        last_step_at=now,
+    )
+    db.add(session)
+    if ticket_kind == "internal":
+        await internal_ticket_service.update_status(
+            db,
+            ticket_id=UUID(ticket_id),
+            status="escalated",
+        )
+    await db.flush()
+    return session