lightrag-memgraph: MemgraphDocStatusStorage missing 4 abstract methods required by lightrag-hku 1.5.5

[antejavor]

What's wrong

MemgraphDocStatusStorage (integrations/lightrag-memgraph/src/lightrag_memgraph/docstatus_impl.py) doesn't implement 4 methods that lightrag-hku's DocStatusStorage base class now requires as abstract:

• get_docs_by_ids
• get_docs_by_statuses_page
• get_full_docs_by_ids
• resolve_doc_source_strict

This breaks LightRAG.__post_init__ (self.doc_status = self.doc_status_storage_cls(...)) at construction time with:

TypeError: Can't instantiate abstract class MemgraphDocStatusStorage with abstract methods get_docs_by_ids, get_docs_by_statuses_page, get_full_docs_by_ids, resolve_doc_source_strict

Reproduces on a clean main checkout (confirmed against commit 8235d6f), pinned lightrag-hku==1.5.5 in the committed lockfile -- not a local dependency-drift artifact. Any code path that constructs a real MemgraphLightRAGWrapper with full_memgraph_persistence=True (the default) hits this immediately, which currently means every real-LLM e2e test in unstructured2graph/lightrag-memgraph that exercises full Memgraph persistence is broken (test_e2e_lightrag.py's entire suite, at minimum).

Acceptance criteria

• Implement the 4 missing methods on MemgraphDocStatusStorage per lightrag-hku's current DocStatusStorage interface
• Confirm unstructured2graph's real-LLM e2e suite (test_e2e_lightrag.py) passes again against a live Memgraph
• Check whether other lightrag_memgraph storage backends (KV, vector) have a similar gap against the current lightrag-hku abstract interface, since this one was only caught by chance

Related

Found while working on #249.