Phase 0: drmprobe findings + A1 corrigendum + worklist update

The drm_info-during-playback probe under Wayland confirmed
KWin IS GL-compositing per frame: Plane 39 rotates triple-
buffered ABGR8888 framebuffers (FB IDs 60/61/66) during
playback. The earlier "0% kwin CPU = direct-scanout" reading
in a1_summary.md was a CPU-blind-spot artifact — Panfrost
shader work isn't visible to top or perf-on-userspace.

Corrigendum added to a1_summary.md preserving the original
text as the on-the-day record.

Worklist: A1 entry updated to point at both summaries.

The probe itself was invasive (drm_info every 3s perturbed
KWin's atomic-commit fast-path, kwin %CPU jumped 0->18 median
and 6 drops appeared) — usable diagnostically but cannot be
embedded in measurement reps.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

phase0_evidence/wayland_baseline_2026-05-03/a1_summary.md

@@ -1,5 +1,22 @@
 # A1 baseline — verdict
 
+> **CORRIGENDUM 2026-05-03 ~17:00 CEST** — the
+> "Major reframing finding" section below interpreted 0 %
+> kwin CPU as "KWin doing nothing per frame, direct-scanout
+> engaged, campaign hypothesis structurally weakened." That
+> interpretation is **wrong**. A subsequent
+> drm_info-during-playback probe (see
+> `drmprobe_findings.md` in this directory) shows Plane 39
+> rotates triple-buffered ABGR8888 framebuffers throughout
+> playback — KWin IS doing per-frame GL composite, but
+> the work is GPU-side (Panfrost) and invisible to top /
+> perf-on-userspace. The campaign's mechanism is intact;
+> the matrix needs GPU-aware metrics. The original text
+> below is preserved as the on-the-day record of what I
+> concluded with insufficient instrumentation.
+
+---
+
 **Three in-session reps of chromium-fourier 149 / brave_drops_test.html
 / Plasma Wayland 6.6.4 + kwin-fourier 6.6.4-3 + qt6-base-fourier
 6.11.0-3 acquired 2026-05-03 14:23–14:31 CEST.**