docs: build round 1 — redox-driver-sys Once regression (sole blocker, fixed)

local/docs/REDBEAR-FULL-SDDM-BRINGUP.md

@@ -66,3 +66,18 @@ Post-login session launch is SDDM's job (`SessionDir=/usr/share/wayland-sessions
 - Full builds re-cooked llvm21 (~1-2h) on every base/relibc bump — fixed in Phase 0.
 - Mesa source/ is an untracked build artifact; durable Mesa changes MUST be patches (Phase 1a).
 - More build-system deficiencies expected during the cook campaign — fix comprehensively as found.
+
+## Build campaign log
+
+### Round 1 (2026-07-24) — redox-driver-sys `Once` regression (sole blocker)
+- `redbear-full --upstream` launched. llvm21 precook OK (long pole done).
+- **SOLE compile failure: `redox-driver-sys`** fails for x86_64-redox with E0425
+  "cannot find type Once" (`pci.rs:20`) — a regression from operator commit
+  `d945483915` (added a Redox-only IOPL `Once` guard without importing it). It is
+  a foundational dep (via `linux-kpi`) of mesa, redox-drm, and every driver, so it
+  cascaded across the whole driver/graphics layer (mesa never reached EGL config).
+- **Fixed:** cfg-gated `use std::sync::Once;` (commit on redox-driver-sys source).
+- Desktop stack (Qt6/KF6/KWin/SDDM) does NOT depend on redox-driver-sys → caches
+  fine in the doomed round. Plan: let round 1 cache the desktop stack, then
+  restart incrementally with the fix so the driver/graphics layer cooks correctly.
+- **Next:** on restart, watch mesa (first real EGL-gate validation) + redox-drm.