feat: move query-related settings to env file for better configuration

• Add env vars for token and chunk settings
• Add token count logging for prompts
• Add token count logging for context
• Move hardcoded values to env variables
• Improve logging clarity and consistency

lightrag/base.py

@@ -54,13 +54,15 @@ class QueryParam:
     top_k: int = int(os.getenv("TOP_K", "60"))
     """Number of top items to retrieve. Represents entities in 'local' mode and relationships in 'global' mode."""
 
-    max_token_for_text_unit: int = 4000
+    max_token_for_text_unit: int = int(os.getenv("MAX_TOKEN_TEXT_CHUNK", "4000"))
     """Maximum number of tokens allowed for each retrieved text chunk."""
 
-    max_token_for_global_context: int = 4000
+    max_token_for_global_context: int = int(
+        os.getenv("MAX_TOKEN_RELATION_DESC", "4000")
+    )
     """Maximum number of tokens allocated for relationship descriptions in global retrieval."""
 
-    max_token_for_local_context: int = 4000
+    max_token_for_local_context: int = int(os.getenv("MAX_TOKEN_ENTITY_DESC", "4000"))
     """Maximum number of tokens allocated for entity descriptions in local retrieval."""
 
     hl_keywords: list[str] = field(default_factory=list)