fix(gate-b): fresh-db install path - conditional guards on plugin-table migrations + dual-path convergence migrations

alembic/versions/0139_reports_folder_id.py

@@ -18,11 +18,31 @@ branch_labels = None
 depends_on = None
 
 
+def _table_exists(conn, table_name: str) -> bool:
+    """True when the table exists (dual-path convergence, Gate B).
+
+    On a fresh install the report_generator plugin SQL migration has not
+    run yet when Alembic reaches this revision — skip instead of failing.
+    The plugin-side convergence migration adds the same column.
+    """
+    row = conn.execute(
+        sa.text("SELECT to_regclass(:tname) IS NOT NULL"),
+        {"tname": f"public.{table_name}"},
+    ).scalar()
+    return bool(row)
+
+
 def upgrade() -> None:
+    conn = op.get_bind()
+    if not _table_exists(conn, "report_templates"):
+        return
     op.add_column("report_templates", sa.Column("folder_id", PGUUID(as_uuid=True), nullable=True))
     op.create_index("ix_report_templates_folder", "report_templates", ["folder_id"])
 
 
 def downgrade() -> None:
+    conn = op.get_bind()
+    if not _table_exists(conn, "report_templates"):
+        return
     op.drop_index("ix_report_templates_folder", table_name="report_templates")
     op.drop_column("report_templates", "folder_id")