Motivation

• Replace blocking local codex exec runs with Codex Cloud sessions so each step executes in an isolated cloud sandbox and can be resumed across process restarts.
• Persist cloud session_id per step so vexdo start --resume can continue in-flight cloud runs and support arbiter fix/resume iterations.

Description

• Rewrote src/lib/codex.ts to implement the cloud lifecycle helpers: submitTask(prompt, {cwd}), resumeTask(sessionId, feedback), pollStatus(sessionId, {intervalMs, timeoutMs}), getDiff(sessionId), and applyDiff(sessionId), plus exec as a convenience wrapper; added CodexTimeoutError and structured CodexError with codes.
• Updated src/commands/start.ts to drive the new cloud flow: submit → poll → diff → review, and added runCloudReviewLoop to handle review/arbiter cycles and call resumeTask when fixes are requested.
• Added CodexErrorCode and session_id?: string to src/types/index.ts and persist session_id to step state via src/lib/state.ts so resume works across restarts.
• Updated tests: new/updated unit tests in test/unit/codex.test.ts for session parsing, polling, timeout and diff handling, and updated integration tests in tests/integration/start.test.ts to validate submit/poll/diff/resume interactions and session_id persistence.

Testing

• Ran targeted tests: npm test -- --run test/unit/codex.test.ts tests/integration/start.test.ts which passed.
• Ran full test suite: npm test which passed all tests (62 passed), and built the CLI with npm run build which succeeded.

Codex Task