Transfer HTTP by model

Stored http_failure_distribution counts for each transfer model. 14 models. 8 store a distribution and 6 do not, so those 6 stay off the page: qwen/qwen3-vl-8b-instruct, mistralai/ministral-8b-2512, bytedance-seed/seed-2.0-mini, qwen/qwen3-vl-32b-instruct, deepseek/deepseek-v4-flash-0731, and xiaomi/mimo-v2.5. The page has 11 model-and-status counts. The highest is 198 for google/gemma-4-26b-a4b-it:free with status 429. The summary http_failures_overall stores 429 as 236, 404 as 169, 200 as 33, None as 4, and 503 as 1. Those totals equal the sum of these per-model counts. Status keys stay as stored, including 200 and None. Bar length is the count against 198. A model with an empty distribution stays off the page.