[Bug]: use_lcc silently drops case-sensitive entity titles from every community

Do you need to file an issue?

• I have searched the existing issues and this bug is not already filed.
• My model is hosted on OpenAI or Azure. (N/A — reproduces independent of model provider; this is a pure data-pipeline bug, not an LLM output issue)
• I believe this is a legitimate bug, not just a question.

Describe the bug

When bringing your own graph (BYOG) with cluster_graph.use_lcc: true (the default), entities whose title contains lowercase characters are silently dropped from every community — with no warning, error, or log line. create_communities reports success and writes N communities, but coverage across all communities can be far less than the number of input entities.

Root cause: graphs/stable_lcc.py's normalize_node_name does html.unescape(name).upper().strip() before computing the largest connected component, and this uppercased form is what gets passed into hierarchical_leiden — so the cluster labels that come back out of cluster_graph() are uppercase. index/workflows/create_communities.py's create_communities() then joins those cluster labels back against entities.title via exact case-sensitive string matching (title_to_entity_id dict lookup, and relationships.merge(level_comms, left_on="source", right_on="title")). Any title that wasn't already all-uppercase fails to match: entity_map["entity_id"] comes back NaN and is dropped via .dropna(), and any community with no matched intra-community edges is dropped entirely by the final inner merge against entity_ids.

This is presumably fine for GraphRAG's own LLM-extraction pipeline, where entity names are conventionally emitted uppercase already — but it's a silent correctness bug for BYOG users bringing case-sensitive titles (e.g. a codebase's real identifier names, which is a very natural BYOG use case).

Steps to reproduce

1. Build a minimal BYOG entities.parquet / relationships.parquet per the BYOG guide with at least one entity title containing lowercase letters (e.g. FooBar, BazQux), and a relationship between two such entities.
2. Configure workflows: [create_communities, create_community_reports] with default cluster_graph.use_lcc: true.
3. Run graphrag index.
4. Inspect output/communities.parquet — the mixed-case entities never appear in any community's entity_ids, despite being connected in relationships.parquet.

Expected Behavior

Every entity that appears in a connected relationship should be assigned to some community, or the pipeline should surface a warning when input entities can't be matched back after LCC normalization.

GraphRAG Config Used

cluster_graph:
  max_cluster_size: 10
  use_lcc: true  # default - triggers the bug
workflows: [create_communities, create_community_reports, generate_text_embeddings]

Logs and screenshots

N/A — the bug produces no error output; it is a silent data-loss issue only visible by comparing entity counts in entities.parquet against total entity_ids coverage across communities.parquet.

Additional Information

• GraphRAG Version: 3.1.0
• Operating System: macOS 26.5.1
• Python Version: 3.12.13
• Related Issues: none found