fix(infinity): Use comma separator for important_kwd to preserve mult…

[liuxiaoyusky]

Problem

The `important_kwd` field in Infinity connector was using mismatched separators:

• Storage: `list2str(v)` uses space as default separator
• Reading: `v.split()` splits by all whitespace

This causes multi-word keywords like `"Senior Fund Manager"` to be incorrectly split into `["Senior", "Fund", "Manager"]`.

Solution

Use comma `,` as separator for both storing and reading, consistent with:

1. The LLM output format in `keyword_prompt.md` ("delimited by ENGLISH COMMA")
2. The `cached.split(",")` in `task_executor.py`

Changes

• `insert()`: `list2str(v)` → `list2str(v, ",")`
• `update()`: `list2str(v)` → `list2str(v, ",")`
• `get_fields()`: `v.split()` → `v.split(",") if v else []`

Impact

This bug affects:

• Python-level reranking weight calculation (`important_kwd * 5`)
• API response keyword display
• Search precision due to fragmented keywords

[liuxiaoyusky]

hello world