Polarization degree from MONK simulations as a function of the cosine of the system inclination angle cos(θ_disk) for a spherical lamppost model (left panel), a conical outflows model (middle panel), and a slab corona model (right panel). The cases cos(θ_disk) = 0 and cos(θ_disk) = 1 represent the edge-on and face-on views of the source, respectively. The green regions indicate the allowed values of the polarization degree: pale green represents the constraint on P from the broadband spectropolarimetric analysis in Sect. 3.3, while saturated green represents the combination of the constraints on P and the system inclination (Sect. 5.3). Because the lamppost and conical geometries yield θ perpendicular to the accretion disk axis, the resulting polarization constraint is set to P < 1.1% in the left and middle panels. Conversely, the slab geometry yields θ parallel to the disk, with P < 2.4%.