llm_completion / llm_acompletion (pageindex/utils.py and
pageindex/index/utils.py) set `litellm.drop_params = True` on the litellm
module. litellm is a process-wide singleton, so this leaked into every other
library sharing it (e.g. a host app like OpenKB that exposes its own litellm
config) and could not be turned off.
Replace the hardcoded `temperature=0` + global `drop_params` with a single
PageIndex-owned per-call kwargs mechanism (config._LLM_PARAMS):
- defaults preserve behavior: {"temperature": 0, "drop_params": True};
- passed per call via **get_llm_params(), never writing litellm's globals, so
nothing leaks into other litellm users in the same process;
- externally configurable: pageindex.set_llm_params(drop_params=False,
temperature=1, num_retries=5, ...) or the PAGEINDEX_DROP_PARAMS env shortcut;
- model/messages are reserved (PageIndex supplies them) and rejected.
