ci: drop pull_request trigger, push alone covers same-repo PRs

push (all branches) already fires for a PR branch on this repo; keeping
pull_request too just ran every job twice on the same commit. GitHub
still attaches the push-triggered run to the PR by SHA regardless of
which event fired it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -1,13 +1,15 @@
 name: CI
 
 # Every push, on every branch — not just main — so build breakage shows up
-# on the first commit of a branch, not only once a PR targets main.
-# pull_request is kept alongside push for fork PRs, where push events never
-# reach this repo.
+# on the first commit of a branch, not only once a PR targets main. No
+# separate pull_request trigger: for a PR from a branch on this same repo,
+# push already fires on that branch, and GitHub attaches the run to the PR
+# by commit SHA regardless of which event triggered it — adding
+# pull_request too would just run every job twice per push. (Re-add it,
+# scoped to forks, only if this repo starts accepting fork PRs — push
+# events from a fork never reach here.)
 on:
   push:
-  pull_request:
-    branches: [main]
 
 env:
   DATABASE_URL: "postgresql://ci:ci@localhost:5432/batchcooking_ci?schema=public"