README: document the GPU wedge fix landing in combined-stable

The stale-rpmh-votes GMU wedge (GMU fw init timeout under bursty GPU
use) is fixed in kernel builds from combined-stable >= 2026-08-14 by
carrying upstream 'drm/msm/a6xx: Fix stale rpmh votes after suspend'
(d9108bfdb746, drm-msm msm-next). This push also triggers the image
rebuild that picks the fix up.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -24,6 +24,17 @@ ambient light/proximity — plus VoLTE calls (both directions) through imsd.
 Verified on exactly one device / one carrier (KPN NL). Reports from other
 carriers are very welcome.
 
+## Known issues
+
+- **Fixed in builds ≥ `7.1.2_git20260814`**: intermittent GPU wedge under
+  bursty use (e.g. browser scrolling) — `a6xx_gmu_resume: GMU firmware
+  initialization timed out` followed by a hangcheck/recovery storm, sometimes
+  taking the session down. The kernel skipped the GPU's RPMh sleep sequence
+  on every GPU suspend (stale power votes broke a later GPU wake); fix
+  carried from upstream ("drm/msm/a6xx: Fix stale rpmh votes after suspend",
+  currently in drm-msm `msm-next`). Occasional
+  `delay in fenced register write (0x8c1)` lines are unrelated and harmless.
+
 ## Flashing
 
 Download `fp6-img.tar.xz` from the latest release and unlock the bootloader