d3d12: dump DRED breadcrumbs when atlas creation fails with device-removed

[dfattal]

Summary

Adds an `ID3D12DeviceRemovedExtendedData` query at the `create_atlas_texture` device-removed branch. When DRED is enabled at device creation, the runtime now logs the last GPU commands recorded by the driver before the device went away — useful for diagnosing the next device-removed crash without having to instrument from scratch.

Background

During the #216 / displayxr-unity#82 investigation, I needed to know which GPU command was removing the device. The standard approach is DRED auto-breadcrumbs, but they're only useful if (a) DRED was enabled before `D3D12CreateDevice` and (b) something on the host side actually queries them when a device-removed surfaces. (a) is on the app/system side; (b) is on us. This PR is (b).

The actual #216 / #82 bug ended up being a plugin-side format mismatch in `CopyTextureRegion`, which DRED couldn't see directly (the driver rejected the command before queuing it as a breadcrumb-tracked op). But the breadcrumb hook is generally useful, and `create_atlas_texture` is the first D3D12 API call after each frame's queue work — so it's the natural place for the runtime to first detect a device-removed and report context.

What's in the PR

• Adds `static void log_dred_state(ID3D12Device *, const char *context)` to `comp_d3d12_renderer.cpp`. Queries `GetAutoBreadcrumbsOutput` + `GetPageFaultAllocationOutput`, logs the last ~16 GPU commands around each node's last-completed marker.
• Calls it from `create_atlas_texture`'s `DXGI_ERROR_DEVICE_REMOVED` branch.
• When DRED isn't enabled, the query returns `DXGI_ERROR_NOT_FOUND` and we log how to turn it on rather than erroring.

How to enable DRED for a given app

Documented in the helper's comment. Three options:

1. Per-process (recommended for an app under active investigation):
   ```cpp
   ID3D12DeviceRemovedExtendedDataSettings *dred_settings = nullptr;
   D3D12GetDebugInterface(IID_PPV_ARGS(&dred_settings));
   dred_settings->SetAutoBreadcrumbsEnablement(D3D12_DRED_ENABLEMENT_FORCED_ON);
   dred_settings->SetPageFaultEnablement(D3D12_DRED_ENABLEMENT_FORCED_ON);
   // ... then D3D12CreateDevice()
   ```
2. Per-app (registry, no code changes):
   `HKLM\SOFTWARE\Microsoft\Direct3D\AppCompat<exe>.exe` with REG_DWORD `AutoBreadcrumbsEnablement = 1` and `PageFaultEnablement = 1`.
3. Globally: Windows Development Build or the DirectX Control Panel.

Test plan

• Builds cleanly on Windows (`scripts/build_windows.bat build`).
• No regression to opaque or transparent rendering paths in casual smoke test (cube_handle_d3d12_win still runs).
• Future: ideally a runtime unit test that intentionally provokes device-removed (out-of-bounds dispatch?) and asserts that breadcrumb output is logged. Not in scope here.

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