App: a launch whose window never drew makes the next use OpenGL (#243)

On some older Intel integrated GPUs (UHD 600, UHD with 2020 drivers)
the graphics driver crashes EffectCraft as its window's DirectX 12 or
Vulkan device is created (exit code 0xC0000005): the process
disappears with no message, and only WGPU_BACKEND=gl helped. A driver
crash can't be caught, so each launch now leaves a marker in the
settings folder until its window draws. A launch that finds the
previous one's marker switches the new Settings ▸ Startup & Repair ▸
Window Graphics (Automatic / OpenGL) to OpenGL and says so in the
status bar. A window that fails to open says the next launch will try
OpenGL. WGPU_BACKEND still wins; macOS has no OpenGL backend, so it
never switches there.

Tests: a_launch_that_never_drew_switches_the_next_to_opengl (app),
window_graphics_is_validated (engine). Checked end to end with a
leftover marker: the app opened on OpenGL with the notice and cleared
the marker.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/preferences.md

@@ -38,6 +38,7 @@ Commands (CLI, MCP, control channel):
 - `general.defaultSpatialLinear`: Default Spatial Interpolation to Linear
 - `startup.showHomeOnLaunch`: Show Home Screen When Launching
 - `startup.offerCrashRecovery`: Offer to Open the Latest Auto-Save After a Crash
+- `startup.windowGraphics`: Window Graphics (`auto` / `gl`), what the desktop window draws with from the next launch. `auto` lets the platform pick (DirectX 12, Vulkan or Metal); `gl` uses OpenGL, with CPU compositing, for graphics drivers that crash with the others. A launch whose window never drew leaves a `launch-pending` marker in the settings folder, and the next launch switches to `gl` and says so (not on macOS, which has no OpenGL backend). `WGPU_BACKEND` overrides both.
 - `project.useTemplate`: New Project Loads Template
 - `project.templatePath`: Template Project
 - `autoSave.enabled`: Automatically Save Projects