* Add document-format crate
* Adapt document-format to merged graph-storage and consolidate errors
* Fix resource write ordering, codec error masking, and export docs
* Remove document-format RFC; tracked in a dedicated PR
* Restructure document-format into gdd/persist/export/resource modules
Split the 963-line lib.rs by responsibility: persist path into persist.rs, resource I/O into resource.rs, export engine into export.rs. Rename the GddV1 layout struct to GddV1Layout and add a GddV1 = Gdd<GddV1Layout> alias.
* Feature-split document-format and graph-storage for minimal builds
* Address PR review: O(1) history-delta lookup and no-default-features test build
* Address PR review: propagate apply_hot_op persist error and assert resource hash
* Make decompression from archive streaming
* Share archive export body between export and export_to_bytes
* Review cleanup
* Export documents with un-retired hot ops losslessly
* Persist last_broadcast_rev in session.json, drop unused last_retired_at
* Move peer_id from manifest to session.json
* Rename gesture to interaction in document-format storage layer