docs(linux): park Slice L at L1 checkpoint

memory/project_linux_graphical.md

@@ -4,6 +4,8 @@
 
 Slice L0 completed at
 `66f114b258c0c37b51a7c0e04ca0d6441f4b1699`.
+Slice L1's implementation checkpoint landed at
+`11501d52cad942850d88f83490710faf1d5cdf28`.
 
 The same `AcDream.App` now builds and publishes for `linux-x64`; there is no
 Linux gameplay or renderer fork.
@@ -44,22 +46,51 @@ Rollback:
 git revert 66f114b258c0c37b51a7c0e04ca0d6441f4b1699
 ```
 
-## Next work — L1
+## L1 implementation checkpoint
 
-Do not claim Linux graphical support merely from publish success. L1 must:
+Canonical seams:
 
-1. start the exact package under the available X11 and Wayland sessions;
-2. capture OS/display/compositor/GPU/driver/OpenGL vendor, renderer, version,
-   mandatory extensions, swap interval, refresh, DPI, and audio backend before
-   renderer construction;
-3. create the OpenGL 4.3 core context and reject missing bindless texture or
-   shader draw parameters with one actionable report;
-4. validate GLFW window/input callbacks, relative mouse/focus, framebuffer
-   sizing, clipboard, and monitor facts;
-5. initialize OpenAL fail-open exactly as current Windows behavior permits;
-6. render a packaged smoke scene, capture a screenshot, and close with zero
-   GL/OpenAL/window debt.
+- `ACDREAM_DISPLAY_PROTOCOL=auto|x11|wayland` selects one immutable backend
+  before `Window.Create`.
+- `GraphicalWindowBackendSelection` configures Silk's exact GLFW backend and
+  makes the packaged GLFW 3.4 native library win over older system installs.
+- `GraphicalCapabilityRecord` captures platform, RID, display protocol, GL
+  identity/extensions/limits, framebuffer, input/window, audio, and terminal
+  ownership into one atomic report.
+- `GraphicalGlFunctionProbe` actively validates bindless texture,
+  draw-parameters plus MDI, SSBO, timer query, sRGB/depth/stencil FBO, and
+  persistent coherent buffer behavior before renderer construction.
+- Unsupported contexts exit with code 4 and a precise report. No legacy
+  renderer or fabricated fallback is introduced.
+- Studio screenshot shutdown is deferred until the completed render frame;
+  accepted and rejected startup paths both report zero terminal ownership.
 
-Historical test-only issue: two installed-DAT App tests still hard-code
-`C:\Turbine\Asheron's Call`. They are not production blockers, but clean them
-before claiming the complete App test suite on a clean Linux runner.
+Evidence:
+
+- native Windows 11 + AMD Radeon RX 9070 XT: every active GL probe passes,
+  OpenAL submits playback and disposes, the packaged smoke frame is intact,
+  and terminal ownership is zero;
+- WSLg X11 and Wayland: packaged GLFW 3.4 and protocol selection are correct,
+  but llvmpipe lacks mandatory `GL_ARB_bindless_texture`;
+- WSLg with `GALLIUM_DRIVER=d3d12` reaches the AMD GPU and OpenGL 4.6, but
+  still lacks mandatory `GL_ARB_bindless_texture`; this is a WSLg/Mesa
+  capability limit, not an acdream package-resolution defect;
+- App tests pass 3,763 / 3 skips; the complete Release suite passes
+  8,826 / 5 skips;
+- checkpoint:
+  `docs/research/2026-07-27-slice-l1-graphical-capability-checkpoint.md`.
+
+Rollback:
+
+```text
+git revert 11501d52cad942850d88f83490710faf1d5cdf28
+```
+
+## Deferred continuation
+
+Do not claim native Linux graphical support from WSLg. Run the exact
+`linux-x64` package on a physical Linux AMD RadeonSI or supported NVIDIA
+driver under the available X11/Wayland sessions. It must pass the same
+capability report, packaged smoke frame, input/window/audio checks, and
+zero-debt shutdown. The user deferred this physical-driver gate and Slices
+L2–L6 on 2026-07-27. L2 has not started; resume at the physical L1 gate.