What type of PR is this?

• feat (new feature)
• fix (bug fix)
• docs (documentation)
• style (formatting, no code change)
• refactor (code change that neither fixes a bug nor adds a feature)
• perf (performance improvement)
• test (adding or updating tests)
• chore (maintenance, tooling)
• build / ci (build or CI changes)

Which issue(s) this PR fixes

Fixes #

What this PR does / why we need it

Entity Linking

• New mem_entities and mem_memory_entity_links tables for efficient entity reverse lookup
• Entity extraction with Chinese city normalization
• Dual-write: entity tables + graph nodes/edges atomically
• Entity-anchored retrieval with configurable boost (default ×1.8)
• Backfill script for migrating existing entity graph data

Scene Nodes & Opinion Evolution

• Trust tier promotion: T4→T3→T2 with confidence thresholds
• Opinion deltas: supporting +0.05, contradicting -0.12, quarantine 0.18
• Three-stage reflection engine with subgraph context + opinion checking
• Scene node consolidation edges linking to source memories
• T2→T3 demotion logic when confidence drops

Dual Trigger Retrieval

• BM25 fulltext search integration alongside vector search
• Dual-trigger retriever uses both anchors for better recall
• Integration tests for entity linking, dual trigger, and reflection

Graph Improvements

• Enhanced entity extractor with Unicode normalization
• Improved graph consolidation logic
• Retry logic for pending graph sync operations