ci: gate cuda san on cuda changes

Signed-off-by: Joe Isaacs <joe.isaacs@live.co.uk>

Author: joseph-isaacs

.github/workflows/cuda.yaml

@@ -12,6 +12,14 @@ on:
     branches: [develop]
   pull_request: { }
   workflow_dispatch: { }
+  schedule:
+    # Nightly full run at 04:00 UTC. Regular CUDA build/test/cudf jobs run on
+    # every PR; the compute-sanitizer matrix is path-filtered to the CUDA
+    # crates for speed. This nightly run (and push-to-develop) restores
+    # sanitizer coverage for changes in dependency crates (vortex-array,
+    # vortex-buffer, encodings, ...) that can affect GPU kernels without
+    # touching vortex-cuda/ itself.
+    - cron: "0 4 * * *"
 
 permissions:
   contents: read
@@ -21,6 +29,29 @@ env:
   RUST_BACKTRACE: 1
 
 jobs:
+  changes:
+    name: "Detect CUDA changes"
+    # Only meaningful on PRs; gates the sanitizer matrix only. Other events
+    # (schedule/push/dispatch) run the sanitizers unconditionally via the
+    # always() guard on cuda-test-sanitizer below.
+    if: github.event_name == 'pull_request'
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      pull-requests: read
+    outputs:
+      cuda: ${{ steps.filter.outputs.cuda }}
+    steps:
+      - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10  # v6
+      - uses: dorny/paths-filter@fbd0ab8f3e69293af611ebaee6363fc25e6d187d  # v4
+        id: filter
+        with:
+          filters: |
+            cuda:
+              - "vortex-cuda/**"
+              - "vortex-test/**"
+              - ".github/workflows/**"
+
   cuda-build-lint:
     if: github.repository == 'vortex-data/vortex'
     name: "CUDA build & lint"
@@ -92,7 +123,10 @@ jobs:
             --verbose
 
   cuda-test-sanitizer:
-    if: github.repository == 'vortex-data/vortex'
+    needs: [changes]
+    if: >-
+      always() && github.repository == 'vortex-data/vortex' &&
+      (github.event_name != 'pull_request' || needs.changes.outputs.cuda == 'true')
     name: "CUDA tests (${{ matrix.sanitizer }})"
     timeout-minutes: 30
     runs-on: runs-on=${{ github.run_id }}/runner=gpu/tag=cuda-test-sanitizer