Add graph expansion and cross-encoder reranking features

- Implemented GraphExpander to enhance search results with related symbols using precomputed neighbors.
- Added CrossEncoderReranker for second-stage search ranking, allowing for improved result scoring.
- Created migrations to establish necessary database tables for relationships and graph neighbors.
- Developed tests for graph expansion functionality, ensuring related results are populated correctly.
- Enhanced performance benchmarks for cross-encoder reranking latency and graph expansion overhead.
- Updated schema cleanup tests to reflect changes in versioning and deprecated fields.
- Added new test cases for Treesitter parser to validate relationship extraction with alias resolution.

codex-lens/src/codexlens/entities.py

@@ -58,6 +58,7 @@ class IndexedFile(BaseModel):
     language: str = Field(..., min_length=1)
     symbols: List[Symbol] = Field(default_factory=list)
     chunks: List[SemanticChunk] = Field(default_factory=list)
+    relationships: List["CodeRelationship"] = Field(default_factory=list)
 
     @field_validator("path", "language")
     @classmethod
@@ -70,7 +71,7 @@ class IndexedFile(BaseModel):
 
 class RelationshipType(str, Enum):
     """Types of code relationships."""
-    CALL = "call"
+    CALL = "calls"
     INHERITS = "inherits"
     IMPORTS = "imports"