feat(kebab-core, kebab-app): p9-fb-25 task 4 — IngestReport.skipped_by_extension + wire schema additive

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

crates/kebab-cli/src/wire.rs

@@ -171,6 +171,7 @@ mod tests {
             unchanged: 0,
             errors: 0,
             duration_ms: 0,
+            skipped_by_extension: std::collections::BTreeMap::new(),
             items: None,
         };
         let v = wire_ingest(&r);