Windows: start Direct3D 12 first, and Vulkan only without a D3D12 GPU (#1190)

* Windows: start Direct3D 12 first, and Vulkan only without a D3D12 GPU

wgpu started Vulkan, D3D12 and OpenGL together and preferred Vulkan, so
every Windows start loaded all installed Vulkan drivers. An old Intel
Vulkan driver (igvk64.dll) crashed 0.10.1 at startup inside the driver.

The app now probes D3D12, then Vulkan, then OpenGL, one backend at a
time, and starts only the first with a hardware adapter (WARP when none
has one). WGPU_BACKEND still wins; graphics.json's "backend" sets the
order by hand; the software renderer (safe mode, the retry) uses D3D12
alone. A new Windows CI job starts the real app under several settings.

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

* CI: a test filter YAML parses

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

* CI: the startup smoke test writes graphics.json where the app reads it

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

* CI: run the WARP shader tests one at a time

WARP's shader JIT (d3d10warp.dll) crashed twice in 124 runs of the gpu
tests with four test threads, with a null read inside its own optimizer
while several devices compiled compute pipelines at once. Serial runs
did not crash.

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

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -306,11 +306,38 @@ jobs:
       - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
         with:
           key: windows-fxc
-      - run: cargo test -p solidcraft-gpu --profile ci --locked
+      # One test at a time: WARP's shader JIT crashes now and then (a null read in
+      # d3d10warp.dll's JIT optimizer, about 1 run in 60) when several devices compile compute
+      # pipelines at once, which the parallel tests do. Minidumps showed it in WARP itself, not
+      # in SolidCraft or FXC; serial runs never hit it.
+      - run: cargo test -p solidcraft-gpu --profile ci --locked -- --test-threads=1
+
+  # The Windows app starts D3D12 first and only the backend it uses (a Vulkan driver crashed the
+  # app at startup on Intel). Start the real app on the runner (its D3D12 adapter is WARP) with
+  # several saved settings and safe mode, and check each draws a frame and quits cleanly.
+  windows-startup:
+    name: Windows app startup
+    needs: changes
+    if: needs.changes.outputs.native == 'true'
+    runs-on: windows-latest
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: windows-startup
+      - name: Backend order and probing on Windows
+        run: cargo test -p solidcraft --profile ci --locked -- startup::tests
+      - name: Build the app
+        run: cargo build -p solidcraft --profile ci --locked
+      - name: Start the app under different settings
+        shell: pwsh
+        run: tools/windows-startup-smoke.ps1 -Exe target/ci/solidcraft.exe
 
   # Preserve the existing check name for branch protection, including docs-only PRs.
   ci:
-    needs: [changes, checks, clippy, build-tests, tests, doc-tests, oracle, windows-fxc]
+    needs: [changes, checks, clippy, build-tests, tests, doc-tests, oracle, windows-fxc, windows-startup]
     if: always()
     runs-on: ubuntu-24.04
     steps:
@@ -325,6 +352,7 @@ jobs:
           DOCS: ${{ needs.doc-tests.result }}
           ORACLE: ${{ needs.oracle.result }}
           WINDOWS_FXC: ${{ needs.windows-fxc.result }}
+          WINDOWS_STARTUP: ${{ needs.windows-startup.result }}
         run: |
           test "$CHANGES" = success
           test "$CHECKS" = success
@@ -335,6 +363,7 @@ jobs:
             test "$DOCS" = success
             test "$ORACLE" = success
             test "$WINDOWS_FXC" = success
+            test "$WINDOWS_STARTUP" = success
           fi
 
   wasm: