When code scanning is enabled, what is one default event that triggers a scan?

Creating a new branch is not a default code scanning trigger event; a subsequent push of commits to that branch is what initiates a scan, not the branch creation itself.

Deleting a branch removes code from active development and does not introduce new code, so it is not a meaningful or default trigger event for code scanning.

Pushing a change is configured as a default trigger event in the code scanning workflow so that every new commit pushed to the repository immediately initiates a security scan, ensuring vulnerabilities introduced by new code are detected as early as possible in the development process.

A branch merge is not a separate default trigger event in code scanning workflow configuration; the push event that results from the merge is what triggers the scan, not the merge action as its own distinct event type.