SerialkompatReports
The serialkompat { reports { … } } block: selects which machine-readable formats the pairwise serialkompatCheck/serialkompatCheckAgainst writes (#122). Modeled on Gradle's own reports { } (a nested block, not flat flags) so formats can grow without a breaking .api change.
Defaults preserve current behavior: json on, sarif off, both under build/serialkompat/. SARIF uses logical locations only (no file:line); GitHub code scanning is out of scope (#122).