Run CI weekly on Sundays

No lockfile is committed (uv.lock is gitignored), so uv resolves
dependencies fresh on every CI run. A scheduled build therefore tests
against current upstream releases and will surface a breaking numpy or
numba version before users hit it — which matters more now that the
numpy upper bound is gone.

Also adds workflow_dispatch so the job can be triggered by hand rather
than only on the cron.

e2e tests stay excluded: they need a GPU, which GitHub-hosted runners
do not provide.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: wrignj08

.github/workflows/ci.yml

@@ -3,6 +3,11 @@ name: CI
 on:
   push:
   pull_request:
+  schedule:
+    # Sundays 00:00 UTC. No lockfile is committed, so uv resolves fresh each
+    # run and this catches upstream releases that break us before users hit them.
+    - cron: "0 0 * * 0"
+  workflow_dispatch:
 
 jobs:
   check: