Phase 0: campaign skeleton, research question pending

Spun off 2026-05-03 from the closed-without-patch
kwin_overlay_subsurface campaign (its phase8_handover.md is
the predecessor). The candidate research question is whether
running an X11 session on PineTab2 reproduces, eliminates, or
transforms the drop-inversion phenomenon that motivated the
predecessor — but the framing is provisional and awaits
operator confirmation before Phase 1 lock.

phase0_findings.md is the substrate doc:
- Predecessor close-out summary (three reasons no patch
  landed; replicate-baseline-first lesson).
- What stays valid from the predecessor (Phase 1 scanout
  archaeology, Phase 2-prime KWin Wayland source-read which
  does NOT transfer to X11, Δ_present-46ms reproducible
  side-finding which is directly testable under X11,
  measurement infrastructure with WAYLAND_DEBUG-specific
  parts that don't transfer).
- Current ohm state (carry-over predecessor tooling, governor
  pin, baloo disabled, kwin-fourier still installed).
- Provisional research question with three plausible
  outcomes (α/β/γ) and four alternate framings the operator
  may have in mind that this question doesn't cover.
- Working-assumption out-of-scope list (no patches, no MRs,
  no Δ_present chase yet).
- Four pre-question Phase 0 deliverables that are unblocked
  regardless of framing: ohm state snapshot, X11-path
  inventory, X11 measurement-tool inventory, A1
  Wayland-baseline rep on this campaign's session for future
  comparison anchor.

worklist.md tracks Phase 0 only. Phase 1 lock awaits the
research question. Discipline carry-overs from
kwin_overlay_subsurface listed (replicate baseline first;
phase discipline; non-upstreaming default; memory
persistence at close).

README.md status banner: Phase 0 in progress, research
question pending operator confirmation.

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

README.md

@@ -0,0 +1,73 @@
+# x11-session-research
+
+> **Status: PHASE 0 — research question pending operator
+> confirmation.** See [`phase0_findings.md`](phase0_findings.md)
+> § "Research question (provisional)" for the candidate framing
+> drafted from the predecessor campaign's close-out. Phase 1
+> lock will not happen before the operator confirms or
+> redirects.
+
+Campaign to investigate X11 session behaviour on PineTab2
+RK3568, in the context of the just-closed
+[`kwin_overlay_subsurface`](../kwin_overlay_subsurface/)
+campaign. Whether running an X11 (Xorg) session on the same
+hardware would (a) reproduce the drop-inversion phenomenon
+that motivated the predecessor, (b) bypass it entirely, or
+(c) introduce a different set of constraints, is the most
+likely campaign question — but this is a working assumption,
+not a locked goal. See `phase0_findings.md`.
+
+## Predecessor
+
+This campaign exists because
+[`../kwin_overlay_subsurface/`](../kwin_overlay_subsurface/)
+closed 2026-05-03 without patch (`phase8_handover.md`). Its
+diagnostic loop terminated at "Phase 0 cage = 0 post-warmup
+drops floor not reproducible at N=3." The natural next move
+across the design surface is to vary the display server (X11
+instead of Wayland) on the same hardware and the same client
+binary, but the operator has not yet confirmed that as the
+campaign's specific question.
+
+## Hardware target (provisional, same as predecessor)
+
+ohm — PineTab2, Rockchip RK3568 (4× Cortex-A55, Mali-G52 MP2,
+hantro G1/G2 VPU). Kernel `6.19.10-danctnix1-1-pinetab2`.
+Mesa 26.0.5. Currently runs KDE Plasma 6.6.4 Wayland.
+
+For an X11-session campaign, ohm needs an Xorg + Plasma X11 (or
+similar X11 desktop) install path verified. As of 2026-05-03,
+the only confirmed display path on ohm is
+`startplasma-wayland`. **Whether Plasma X11, an alternate X11
+desktop (XFCE, openbox, lightweight WM), or Plasma running
+under a Wayland-Xorg shim is in scope is part of the research
+question to be locked.**
+
+## Carry-overs from predecessor (still active on ohm)
+
+Per `kwin_overlay_subsurface/phase1_evidence/ohm_tooling_revert_log.md`:
+
+- `qt6-base-fourier 1:6.11.0-3` installed.
+- `kwin-fourier 1:6.6.4-3` installed.
+- CPU governor pinned to `performance` (was `conservative`).
+- Baloo permanently disabled
+  (`Indexing-Enabled=false` in `~/.config/baloofilerc`).
+- `drm-info 2.9.0-1` installed.
+
+These were not reverted at the predecessor's close-out. This
+campaign inherits them unless an explicit revert is part of
+the design.
+
+## Non-upstreaming default
+
+Inherited from the predecessor and from `ohm_gl_fix`. Bug
+reports + MRs are explicit operator-tasked decisions, not
+background process steps.
+
+## File map (will grow)
+
+| File | What it is |
+|---|---|
+| `README.md` | This file. |
+| `phase0_findings.md` | Substrate from the predecessor + the candidate research question. **Awaits operator confirmation/redirect on the question itself.** |
+| `worklist.md` | Phase-by-phase task list. Phase 0 only as of campaign start. |