Add non-blocking glTF validator CI step

Agent-Logs-Url: https://github.com/syoyo/tinygltf/sessions/12f39a87-22c8-439b-aa5e-c72eade32ee8

Co-authored-by: syoyo <18676+syoyo@users.noreply.github.com>

.github/workflows/ci.yml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ce6a7f7..560cf33 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,7 +26,7 @@
         uses: actions/checkout@v4
 
       - name: Configure
-        run: cmake -B build -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON
+        run: cmake -B build -DTINYGLTF_BUILD_LOADER_EXAMPLE=ON -DTINYGLTF_BUILD_V3_VALIDATOR_TOOL=ON
 
       - name: Build
         run: cmake --build build
@@ -37,6 +37,17 @@
       - name: Run tests
         run: ctest --test-dir build --output-on-failure
 
+      - name: Run v3 validator on tracked glTF files
+        continue-on-error: true
+        run: |
+          rc=0
+          while IFS= read -r path; do
+            echo "::group::Validate ${path}"
+            ./build/tools/validator/tinygltf3-validator "${path}" || rc=1
+            echo "::endgroup::"
+          done < <(git ls-files '*.gltf')
+          exit $rc
+
   # Linux x64 - Clang 21
   linux-clang-x64:
     runs-on: ubuntu-24.04