fix: checkout easy-gl sibling repo for CNA's EASYGL backend in CI

Configure now gets past SDL3's X11/XTEST checks (previous 2 commits)
but hard-fails one step later: "CNA: Missing sibling repository
'easy-gl'". CNA's CNA_BACKEND_EASY_GL option -- enabled by every entry
in this job's backend matrix, since the single "Configure editor" step
always configures both EASYGL and Vulkan regardless of which one is
the matrix's "primary" backend that run -- requires a sibling
../easy-gl checkout (add_subdirectory(../easy-gl), not a submodule of
CNA). ci.yml checked out cna and sharp-runtime as siblings but never
easy-gl.

Added a "Checkout easy-gl" step to both the editor matrix job and the
Editor (EASYGL) ASan+UBSan job, mirroring the existing cna/sharp-runtime
checkout pattern exactly. Pinned to
62c0a248a6c4144abaf92c0530cc2a2395e5fd37 -- the current tip of this
sandbox's own easy-gl sibling checkout, the only revision confirmed to
build successfully together with a CNA checkout locally (this sandbox's
local cna is a newer revision than CI's pinned d0c21ee6, so this isn't
a guarantee the exact pairing CI uses is compatible, only the best
available evidence; a real CI run will confirm or reveal a version
mismatch directly).

Author: robertvokac

.github/workflows/ci.yml

@@ -8,10 +8,13 @@
 # fixture. For exact live counts run `ctest -N`; they are deliberately not
 # hard-coded here.
 #
-# The editor job below checks out the two required sibling repositories beside
-# this checkout, exactly matching the root CMake project layout
-# (`../cna`, `../sharp-runtime`). EASYGL runs the complete root CTest suite,
-# while the Vulkan matrix entry always configures and builds the real editor.
+# The editor job below checks out the three required sibling repositories
+# beside this checkout, exactly matching the root CMake project layout
+# (`../cna`, `../sharp-runtime`, `../easy-gl` -- the last one only because
+# CNA's own CNA_BACKEND_EASY_GL option, which every matrix entry enables,
+# requires it as a sibling checkout). EASYGL runs the complete root CTest
+# suite, while the Vulkan matrix entry always configures and builds the real
+# editor.
 # Vulkan is enabled for the explicit manual SYS-W8-05 qualification run;
 # WebGPU remains gated pending its own pixel-qualified runner.
 
@@ -261,6 +264,20 @@ jobs:
           path: sharp-runtime
           ref: 5cdaafb2bace46dce5393da21dad9ff9f8ad3c58
 
+      # CNA's CNA_BACKEND_EASY_GL option (which the EASYGL backend this job
+      # matrix builds turns on) requires a sibling 'easy-gl' checkout --
+      # CNA's own CMakeLists.txt hard-fails configure without it
+      # ("Missing sibling repository 'easy-gl'"). Every matrix entry needs
+      # it, not just EASYGL: the single "Configure editor" step below always
+      # configures both backends (it's followed by both an EASYGL-only build
+      # step and an unconditioned "Build Vulkan editor" step).
+      - name: Checkout easy-gl
+        uses: actions/checkout@v4
+        with:
+          repository: openeggbert/easy-gl
+          path: easy-gl
+          ref: 62c0a248a6c4144abaf92c0530cc2a2395e5fd37
+
       - name: Install editor build dependencies
         run: |
           sudo apt-get update
@@ -351,6 +368,16 @@ jobs:
           path: sharp-runtime
           ref: 5cdaafb2bace46dce5393da21dad9ff9f8ad3c58
 
+      # See the "editor" job's own "Checkout easy-gl" step comment: CNA's
+      # CNA_BACKEND_EASY_GL option (which this EASYGL-specific job enables)
+      # requires a sibling 'easy-gl' checkout or configure hard-fails.
+      - name: Checkout easy-gl
+        uses: actions/checkout@v4
+        with:
+          repository: openeggbert/easy-gl
+          path: easy-gl
+          ref: 62c0a248a6c4144abaf92c0530cc2a2395e5fd37
+
       - name: Install editor build dependencies
         run: |
           sudo apt-get update