The yaml default `azure_openai_auth_mode: azure_cli` was silently
overwriting `AZURE_OPENAI_AUTH_MODE` exported by the user, because
`configure_clients()` treats any non-empty config value as an explicit
override. Switching the three auth_mode defaults (shared / optimizer /
target) to "" lets `_clean()` drop them and restores the intended
fallback chain: yaml → env var → module default ("azure_cli").
Also update README and .env.example to document the openai_compatible
mode introduced in d5c5b61, and remove the misleading `OPENAI_API_KEY`
snippet — SkillOpt reuses the `AZURE_OPENAI_*` env vars in this mode.
- Skill optimization framework with training loop analogy
- 11 benchmarks, 4 model backends (Azure OpenAI, Claude, Codex, Qwen)
- WebUI for browser-based training control
- Pluggable architecture for extending benchmarks and backends
