Describe the bug

execution_info shows total_cost_USD: 0.0 for OpenRouter calls that cost small amounts. Two issues:

1. Rounding problem: Small costs <0ドル.0 get rounded down to 0.0 instead of showing the actual amount
2. Missing tokens: prompt_tokens only counts the user prompt, completely ignores the webpage content that gets fed to the LLM

To Reproduce

Using OpenRouter with gpt-4.1 model, for a decent size webpage scraping call, the exec info shows:

[
 {
 "node_name": "GenerateAnswer",
 "total_tokens": 213,
 "prompt_tokens": 193,
 "completion_tokens": 20,
 "successful_requests": 1,
 "total_cost_USD": 0.0,
 "exec_time": 1.89
 },
 {
 "node_name": "TOTAL RESULT", 
 "total_tokens": 213,
 "prompt_tokens": 193,
 "completion_tokens": 20,
 "successful_requests": 1,
 "total_cost_USD": 0.0,
 "exec_time": 8.98
 }
]

But checking OpenRouter shows I actually got charged (even if small amounts like 0ドル.007-0.01 per call).

Expected behavior

• total_cost_USD should show the actual cost, not 0.0
• prompt_tokens should include webpage content tokens, not just the user prompt (193 tokens seems way too low for a full webpage + prompt)

Additional context

Input token usage issue is actaully for manual cost tracking as a fallback which is now impossible.