feat(kebab-app): p9-fb-25 task 5 — Skipped warnings + skipped_by_extension aggregation

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

crates/kebab-app/tests/skip_reason.rs

@@ -0,0 +1,43 @@
+//! p9-fb-25 task 5: skipped per-asset items must carry a human-readable
+//! reason in `warnings`, and the report's `skipped_by_extension` must
+//! aggregate by lowercase extension.
+
+mod common;
+
+use common::TestEnv;
+
+#[test]
+fn unsupported_extension_skip_carries_warning_and_is_aggregated() {
+    let env = TestEnv::lexical_only();
+    let workspace_root = std::path::PathBuf::from(&env.config.workspace.root);
+    std::fs::write(workspace_root.join("legacy.docx"), b"unsupported").unwrap();
+    std::fs::write(workspace_root.join("Makefile"), b"unsupported").unwrap();
+
+    let report = kebab_app::ingest_with_config(
+        env.config.clone(),
+        env.scope(),
+        false,
+    ).unwrap();
+
+    let items = report.items.as_ref().expect("items array populated");
+    let docx_item = items
+        .iter()
+        .find(|i| i.doc_path.0.ends_with("legacy.docx"))
+        .expect("docx in items");
+    assert_eq!(docx_item.kind, kebab_core::IngestItemKind::Skipped);
+    assert_eq!(
+        docx_item.warnings,
+        vec!["unsupported media type: .docx".to_string()],
+    );
+    let makefile_item = items
+        .iter()
+        .find(|i| i.doc_path.0.ends_with("Makefile"))
+        .expect("Makefile in items");
+    assert_eq!(makefile_item.kind, kebab_core::IngestItemKind::Skipped);
+    assert_eq!(
+        makefile_item.warnings,
+        vec!["unsupported media type: <no-ext>".to_string()],
+    );
+    assert_eq!(report.skipped_by_extension.get("docx").copied(), Some(1));
+    assert_eq!(report.skipped_by_extension.get("<no-ext>").copied(), Some(1));
+}