ci(test): validate intra-doc links in private items

Author: claude

test.sh

@@ -62,7 +62,11 @@ unit() (
     skip_args+=(--skip "$name")
   done
   run_if "${LINT:-true}" cargo clippy "$@" -- -D warnings
-  run_if "${DOC:-false}" cargo doc "$@"
+  # `--document-private-items` lets rustdoc validate intra-doc links inside
+  # private items; the `rustdoc::private_intra_doc_links` lint, promoted to an
+  # error by `-D warnings`, still rejects public-to-private links.
+  run_if "${DOC:-false}" env RUSTDOCFLAGS="-D warnings ${RUSTDOCFLAGS:-}" \
+    cargo doc --document-private-items "$@"
   run_if "${BUILD:-true}" cargo build ${build_flags[@]+"${build_flags[@]}"} "$@"
   if [[ ${#skip_args[@]} -gt 0 ]]; then
     run_if "${TEST:-true}" cargo test ${test_flags[@]+"${test_flags[@]}"} "$@" -- "${skip_args[@]}"