Feat: Redesign and refactor agent module (#9113)

### What problem does this PR solve?

#9082 #6365

<u> **WARNING: it's not compatible with the older version of `Agent`
module, which means that `Agent` from older versions can not work
anymore.**</u>

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

rag/app/email.py

@@ -40,7 +40,7 @@ def chunk(
     eng = lang.lower() == "english"  # is_english(cks)
     parser_config = kwargs.get(
         "parser_config",
-        {"chunk_token_num": 128, "delimiter": "\n!?。；！？", "layout_recognize": "DeepDOC"},
+        {"chunk_token_num": 512, "delimiter": "\n!?。；！？", "layout_recognize": "DeepDOC"},
     )
     doc = {
         "docnm_kwd": filename,