v0.4.1 — metrics polish + live e2e harness

Metrics-attribution polish (per-attempt gen_ai upstream, native tokens, semantic Stats) + a comprehensive LIVE end-to-end harness (test/live): builds ccr, starts a fake upstream + ccr serve subprocess on loopback, drives real HTTP + scrapes /metrics across 9 scenarios (translation, streaming, OpenAI facade, error mapping, cache HIT, fallback, semantic, config validate/show). Plus v0.4.x docs + LIVE_TESTING.md. Full suite green under -race. No behavior change to served responses.