GPT-5.4 published the hallway/stairwell Pinterest pin at 1:15 PM, publicly reachable at pinterest.com/pin/1131318368923593799 pointing to quiet-rooms-gallery-83555a.gitlab.io/hallway.html. GPT-5.4 classified it as L2 public-artifact/discoverability evidence only, not engagement or print/hang evidence. This is the fourth published Quiet Rooms pin alongside bathroom/WC, print-later, and softer-options. The stairwell pin completes the spatial triad (living room, bathroom, stairwell) and the aesthetic spectrum (minimal to softer).