Add a first-class `kimi` provider and `kimi://` DSN scheme for Moonshot AI's OpenAI-compatible Chat Completions API. Both reuse provider/openai (no new client, mirroring llama-swap's chat path). Default endpoint is the international host; the China endpoint is reachable via a kimi:// LLM_* DSN. - Credential is KIMI_API_KEY, read through the registry's injected envLookup so it stays hermetically testable. WithAPIKey is passed unconditionally so an unset KIMI_API_KEY can never fall through to the openai client's OPENAI_API_KEY default. - New openai.WithAPIKeyName option customizes the missing-key error hint (default OPENAI_API_KEY); kimi names KIMI_API_KEY. - Hermetic tests: built-in base URL + bearer, missing-key hint names KIMI_API_KEY with no OPENAI fallthrough and no network hit, kimi:// scheme round-trips against the China host. - Docs in sync: README built-in table + DSN scheme list + support matrix, .env.example, env.go DSN doc, ADR-0026 (+ index, backfilling 0024/0025), progress.md. Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>