feat(codex): support reasoning effort targets config

[christso]

Summary

Codex targets can now configure SDK reasoning effort from targets.yaml, so eval runs can use env-backed settings like CODEX_MODEL=gpt-5.5 with CODEX_REASONING_EFFORT=low. The wire field remains snake_case-only as model_reasoning_effort, resolves to internal modelReasoningEffort, and is forwarded into startThread with the SDK-supported enum values.

The Codex SDK dependency was stale in the lockfile at 0.104.0, even though the shell codex binary was 0.136.0. This PR bumps @openai/codex-sdk/bundled @openai/codex to 0.136.0 and makes the SDK provider honor the existing Codex executable target setting via codexPathOverride, so targets can use profile shims such as codex-eng.

The root Codex target now includes executable, model, and model_reasoning_effort env bindings, and the Codex target docs list all three fields.

Verification

• bun test packages/core/test/evaluation/providers/targets.test.ts
• bun test packages/core/test/evaluation/providers/codex-sdk.test.ts
• bun test packages/core/test/evaluation/validation/targets-validator.test.ts
• bunx biome check .agentv/targets.yaml apps/web/src/content/docs/docs/targets/coding-agents.mdx apps/cli/package.json packages/core/package.json packages/core/src/evaluation/providers/codex.ts packages/core/src/evaluation/providers/targets.ts packages/core/src/evaluation/providers/types.ts packages/core/src/evaluation/validation/targets-validator.ts packages/core/test/evaluation/providers/codex-sdk.test.ts packages/core/test/evaluation/providers/targets.test.ts packages/core/test/evaluation/validation/targets-validator.test.ts
• bun run build

Smoke passed with:

AGENT_TARGET=codex LLM_TARGET=azure GRADER_TARGET=azure CODEX_EXECUTABLE=codex-eng CODEX_MODEL=gpt-5.5 CODEX_REASONING_EFFORT=low CODEX_LOG_DIR=.agentv/logs/codex bun apps/cli/src/cli.ts eval evals/self/azure-smoke.eval.yaml --target codex --workers 3

Result: PASS (2/2, mean 100%). Artifacts were written to:

• .agentv/results/runs/default/2026-06-03T11-24-27-757Z
• .agentv/results/runs/default/2026-06-03T11-24-27-757Z/index.jsonl
• .agentv/results/otel-2026-06-03T11-24-27-757Z.json
• .agentv/logs/codex/2026-06-03T11-24-28-160Z_codex_simple-math_attempt-1_985a8833.log
• .agentv/logs/codex/2026-06-03T11-24-28-182Z_codex_capital-of-france_attempt-1_2faff0e9.log

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