CI: Pin Windows runners to windows-2022 (VS 2026 breaks Conan/pixi builds) (#1156)

GitHub's `windows-latest` image now ships Visual Studio 2026 (MSVC 19.5),
which breaks both Windows CI jobs:

- `cmake Windows`: `conan profile detect` selects msvc 195, so Conan asks
  CMake for the "Visual Studio 18 2026" generator, which the installed
  CMake cannot create. The vendored foonathan-lexy dependency fails to
  build with "Could not create named generator Visual Studio 18 2026".

- `Pixi (conda)`: `cmake ..` defaults to the "Visual Studio 17 2022"
  generator, which is no longer present ("could not find any instance of
  Visual Studio").

Pin both jobs to windows-2022 (VS 2022 / MSVC 19.3x) to restore green CI.
Also set fail-fast: false on the pixi matrix so the ubuntu leg is no
longer masked by a Windows failure.

Co-authored-by: Davide Faconti <davide.faconti@gmail.com>

Author: wooksong

.github/workflows/cmake_windows.yml

@@ -16,7 +16,10 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [windows-latest]
+        # Pinned to windows-2022: windows-latest now ships Visual Studio 2026
+        # (MSVC 19.5), which makes Conan request the "Visual Studio 18 2026"
+        # generator that the installed CMake cannot create.
+        os: [windows-2022]
         build_type: [Release, Debug]
 
     steps:

.github/workflows/pixi.yaml

@@ -14,9 +14,13 @@ concurrency:
 jobs:
   pixi_conda_build:
     strategy:
+      fail-fast: false
       matrix:
         os:
-          - windows-latest
+          # Pinned to windows-2022: windows-latest now ships Visual Studio 2026,
+          # but cmake defaults to the "Visual Studio 17 2022" generator, which is
+          # no longer present ("could not find any instance of Visual Studio").
+          - windows-2022
           - ubuntu-latest
     runs-on: ${{ matrix.os }}
     steps: