docs: 更新 L1A 增量功能说明及 ETL 文档

ETL/README.md

@@ -1,7 +1,23 @@
-L1A output_arena/iframe_network.json -> L1A.sqlite(Primary Key: match_id)
+# ETL Pipeline Documentation
+
+## 1. L1A (Raw Data Ingestion)
+**Status**: ✅ Supports Incremental Update
+
+This script ingests raw JSON files from `output_arena/` into `database/L1A/L1A.sqlite`.
+
+### Usage
+```bash
+# Standard Run (Incremental)
+# Only processes new files that are not yet in the database.
+python ETL/L1A.py
+
+# Force Refresh
+# Reprocesses ALL files, overwriting existing records.
+python ETL/L1A.py --force
+```
 
 L1B demoparser2 -> L1B.sqlite
 
 L2 L1A.sqlite (+L1b.sqlite) -> L2.sqlite
 
-L3 Deep Dive.
+L3 Deep Dive