test(llm): re-record golden scenarios against live providers

Verifies the new Usage mapper code against live provider responses for
OpenAI Chat, OpenAI Responses, Anthropic, Gemini, DeepSeek, and
TogetherAI — 16 fresh recordings, all assertions pass. No existing
cassettes were modified; these populate test slots that were previously
skipped in replay mode.

Recorded via:
    set -a; source .env.recorded.local; set +a
    RECORD=true bun test test/provider/*.recorded.test.ts

Redactor stripped all auth headers; no secrets in the cassettes.