feat: persist task lane across submits and session reloads

Task lane questions/actions are now saved to a pending_task_lane JSONB
column on ai_sessions, restoring them on session switch or page reload.
Partial submit no longer force-clears the lane — the AI response
controls what stays. Also removes redundant "New Session" button from
the sidebar (dashboard already provides this).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/alembic/versions/fc01_add_pending_task_lane.py

@@ -0,0 +1,30 @@
+"""add pending_task_lane to ai_sessions
+
+Revision ID: fc01a1b2c3d4
+Revises: fb1481317ff6
+Create Date: 2026-03-27
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import JSONB
+
+revision = "fc01a1b2c3d4"
+down_revision = "fb1481317ff6"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "ai_sessions",
+        sa.Column(
+            "pending_task_lane",
+            JSONB,
+            nullable=True,
+            comment="Current task lane state: {questions: [...], actions: [...]}",
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("ai_sessions", "pending_task_lane")

backend/app/models/ai_session.py

@@ -209,6 +209,10 @@ class AISession(Base):
         JSONB, nullable=False, default=list,
         comment="Full LLM message history for context continuity",
     )
+    pending_task_lane: Mapped[Optional[dict[str, Any]]] = mapped_column(
+        JSONB, nullable=True,
+        comment="Current task lane state: {questions: [...], actions: [...]}",
+    )
 
     # ── Branching ──
     is_branching: Mapped[bool] = mapped_column(

backend/app/schemas/ai_session.py

@@ -228,6 +228,7 @@ class AISessionDetail(AISessionSummary):
     ticket_data: dict[str, Any] | None = None
     steps: list[AISessionStepResponse] = []
     conversation_messages: list[dict[str, Any]] = []  # Chat sessions store messages here
+    pending_task_lane: dict[str, Any] | None = None
     is_branching: bool = False
     active_branch_id: str | None = None
 

backend/app/services/unified_chat_service.py

@@ -286,6 +286,15 @@ async def send_chat_message(
                 except Exception:
                     logger.exception("Failed to create fork within branch for session %s", session.id)
 
+            # Persist task lane state on session
+            if branch_questions_data or branch_actions_data:
+                session.pending_task_lane = {
+                    "questions": branch_questions_data or [],
+                    "actions": branch_actions_data or [],
+                }
+            else:
+                session.pending_task_lane = None
+
             suggested_flows = extract_suggested_flows(
                 await rag_search(query=message, account_id=account_id, db=db, limit=8)
             )
@@ -393,6 +402,15 @@ async def send_chat_message(
             logger.exception("Failed to create fork for session %s", session_id)
             # Fork failed but chat message still sent — don't break the response
 
+    # Persist task lane state on session
+    if questions_data or actions_data:
+        session.pending_task_lane = {
+            "questions": questions_data or [],
+            "actions": actions_data or [],
+        }
+    else:
+        session.pending_task_lane = None
+
     suggested_flows = extract_suggested_flows(rag_results)
 
     return display_content, suggested_flows, session, fork_metadata, actions_data, questions_data