fix(ci): make ci.yml callable as reusable workflow (workflow_call)

deploy.yml invokes ci.yml as its 'test' gate via 'uses:', which requires
a workflow_call trigger. Without it the entire Deploy workflow was invalid
and failed before deploying.

Author: obielin

.github/workflows/ci.yml

@@ -5,6 +5,8 @@ on:
     branches: [main, develop]
   pull_request:
     branches: [main, develop]
+  # Allow this workflow to be called by deploy.yml as a reusable "test" gate.
+  workflow_call:
 
 jobs:
   python: