fix: pass max_retries and timeout_sec from YAML config to LLMClient

[dennis-lynch-nv]

Problem

LlmConfig dataclass and _parse_llm_config() in config.py did not read max_retries or timeout_sec from the YAML config file. Additionally, LLMClient.from_rc_config() in client.py did not forward these values to LLMConfig.

This caused the LLMClient to always use the hardcoded default of 3 retries and 300s timeout regardless of what the user set in config.arc.yaml.

For example, setting max_retries: 8 in config had no effect — the client still retried only 3 times.

Fix

1. config.py — Added max_retries and timeout_sec fields to the LlmConfig dataclass, and parse them in _parse_llm_config()
2. client.py — LLMClient.from_rc_config() now forwards both values to LLMConfig

Verification

from researchclaw.config import load_config
from researchclaw.llm.client import LLMClient

cfg = load_config('config.arc.yaml')  # max_retries: 8, timeout_sec: 1900
client = LLMClient.from_rc_config(cfg)
assert client.config.max_retries == 8   # Previously: 3
assert client.config.timeout_sec == 1900  # Previously: 300