feat(review-tutor): add Codex connector

[ElbertePlinio]

Changed

• add Codex model discovery from codex debug models, with version/catalog bounds, per-entry validation, and safe reviewer-effort filtering
• bound both sequential discovery calls with a 10-second timeout and AbortSignal
• run codex exec through the shared read-only runner boundary with a minimal environment
• keep completion state per run on a shared connector and parse Codex JSONL completion, usage, and mapped/redacted failures
• redact provider URLs, request IDs, Cloudflare rays, and thread IDs on shared process-failure paths
• register Codex only behind reviewTutorHarnessConnectors
• add fake-only discovery, parser, runner, registry, redaction, and protocol-boundary coverage

Tested

• npx vitest run packages/review-tutor/test — 316 passed
• cd packages/review-tutor && npm run typecheck — passed
• bun run check — 607 passed, 25 skipped; lint, coverage, typecheck, and builds passed

Not tested

• real unauthenticated/rate-limited Codex accounts
• macOS or Windows

Risk

• risk class: serious backend
• process boundary and provider-error handling; mitigated by exact argv/env/signal tests, read-only sandboxing, fake-only failure fixtures, redaction checks, and shared-connector sequential-run coverage

Smoke

• Linux local smoke from the original implementation round in a temporary Git repository, discovered gpt-5.6-sol, effort low
• exit 0; answer ok; no secret-like text detected in captured events
• no real codex invocation was run during this review-fix round

PR 3 of the Review Tutor connector plan; stacked on PR #76.

Refs #63

[ElbertePlinio]

Ready for human review at 820026d (stack: #76 → #77 → #78). Panel: Opus correctness (3×P2 + P3s → fixed, mutation-verified), Grok security (2×P3 → fixed); round 2 closed two P2s (fallback failure messages now go through the shared redact(); server-extension test no longer spawns the real codex — PATH-shim proof). Real smoke: gpt-5.6-sol/low → "ok". Deferred P3s in #79. CI green.