[vsimko]

Summary

• Add a Solr 10.1-only integration case for includeStoredFields=true.
• Create a disposable stored-only string field and a separate docValues sort field, then assert that Export returns the stored value.
• Keep Solr 8/9 explicitly outside this behavior claim.
• Reconcile docs/export.md, docs/api-coverage.md, docs/compatibility.md, docs/api-inventory.json, and the roadmap with the exact Solr 10.1 evidence.

Closes #258

Validation

• The initial test commit passed CI run #648 (30/30), including standalone and security integration on Solr 10.1.0 / Node 20, 22, and 24.
• This PR is opened on the latest master base to run CI against the complete updated documentation and inventory.