feat: add codex executor config support

[davidhonig]

Summary

Adds a codex executor for Waza eval runs, backed by the local Codex CLI and the user’s existing ~/.codex/config.toml / auth setup.

Changes

• Add internal/execution/CodexEngine using codex exec.
• Support defaults.engine: codex in .waza.yaml.
• Allow Codex model defaults from ~/.codex/config.toml when no Waza model is configured.
• Support .waza.yaml / eval YAML model_reasoning_effort, passed to Codex as -c model_reasoning_effort=....
• Show Model: default (Codex config) when Codex model is intentionally defaulted.
• Add Codex option to waza init.
• Update eval/project schemas and docs for Codex configuration.
• Preserve follow-up prompt context using codex exec resume.
• Parse Codex JSON events into Waza transcript, tool-call telemetry, and token usage.
• Explicitly reject Codex skill_invocation grader / trigger telemetry paths that the Codex CLI does not expose.

Validation

• go test ./...
• cd site && npm run build
• Manual MCL eval smoke test with Codex config confirmed:
  • configured model is displayed
  • model_reasoning_effort reaches Codex
  • Codex starts successfully through Waza

[davidhonig]

@microsoft-github-policy-service agree