magpie-issue-reproducer

For a single <issue-tracker> issue identifying a code-level bug, extract the reporter's example code from the issue body, adapt it to run on the current <default-branch>, execute via <runtime>, and compose a verdict.json describing the observed behaviour vs the expected failure. Read-only on the tracker — produces evidence, never posts. Invoked by issue-triage and issue-reassess; can also be run standalone.