dmabuf-modifier-triage campaign scaffold

Focused triage of marfrit/libva-multiplanar#1 — dmabuf-wayland green
on ohm independent of decoder backend. Locked question: identify the
layer responsible (libva / ffmpeg / KWin / Mesa-panfrost / kernel)
and file upstream where appropriate. Performance is explicitly out of
scope — user has working slow path via vo=gpu hwdec=v4l2request.

Phase 0 deliverables: vaExportSurfaceHandle + AVDRMFrameDescriptor
modifier captures, Wayland linux-dmabuf-v1 advertise snapshot, pacman
upgrade timeline review for the iter5→iter8 regression window, and
stock-kwin A/B isolating kwin-fourier as a candidate.

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

.gitignore

@@ -0,0 +1,25 @@
+references/
+
+# Inside phase*_evidence/ track narrative .md notes; ignore raw captures.
+phase*_evidence/**/*.txt
+phase*_evidence/**/*.log
+phase*_evidence/**/*.pcap
+phase*_evidence/**/*.strace
+phase*_evidence/**/*.bin
+phase*_evidence/**/*.gz
+phase*_evidence/**/*.zst
+phase*_evidence/**/*.dat
+phase*_evidence/**/*.trace
+phase*_evidence/**/*.json
+phase*_evidence/**/*.ftrace
+phase*_evidence/**/*.jpg
+phase*_evidence/**/*.png
+phase*_evidence/**/*.nv12
+phase*_evidence/**/*.yuv
+phase*_evidence/**/*.tsv
+phase*_evidence/**/*.strace*
+phase*_evidence/**/libva.trace.*
+
+*.log
+*.pcap
+*.strace