Make the inert display_powersave drain-gate seam real. While the host's primary display is asleep/in powersave the deferred-processing drain gate opens (debounced ~120s, wake closes immediately); when display state can't be reliably detected the condition reports undetectable and the owner falls back to the time window — it never claims asleep when it can't tell. New solstone/think/display_powersave.py: a read-only, exception-total detector (Linux DRM sysfs dpms aggregation; macOS CoreGraphics CGDisplayIsAsleep via ctypes + a pmset-log fallback when there is no window-server session) plus an in-memory monotonic-clock debouncer. evaluate_display_powersave/evaluate_drain_gate become pure functions of a passed-in display reading; only the supervisor gate-tick polls the detector (and only when the condition is enabled), while the health surface reads the last-known snapshot, so health reads do no OS I/O and never advance the debounce. A sticky display_powersave_detectable field is exposed on the health surface (data only; never feeds gate open/closed). Supersedes note: the parent spec names the Linux mechanism "X11 DPMS" and calls Wayland the undetectable case. This beneficially supersedes that — the DE-independent sysfs DRM signal works under both X11 and Wayland on atomic drivers (amdgpu/i915/nouveau), narrowing the undetectable population from "all of Wayland" to "NVIDIA-proprietary / headless". Recorded so a future reader does not "fix" it back to X11-only. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>