Re-review on push: expand pull_request trigger to opened+reopened+synchronize

The reverted Codex workflow originally fired only on `pull_request: opened`,
forcing re-reviews to go through the `/ai-review` issue_comment path. That path
breaks during workflow-revert PRs like this one: issue_comment events use the
default branch's workflow YAML, so until the PR merges, re-trigger comments hit
the old broken workflow.

Adding `reopened` and `synchronize` lets a normal `git push` (or close+reopen)
fire the workflow against the PR's own YAML, so the PR self-validates on each
update without the comment-trigger detour.

Side benefit beyond this PR: every future PR auto-rereviews on push instead of
requiring a manual `/ai-review` comment per round.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: igerber

.github/workflows/ai_pr_review.yml

@@ -2,7 +2,7 @@ name: AI PR Review (Codex)
 
 on:
   pull_request:
-    types: [opened]
+    types: [opened, reopened, synchronize]
   issue_comment:
     types: [created]
   pull_request_review_comment: