feat(runtime): align agent step CWD to REPO_DIR (eliminate step-artifact isolation)

[khaliqgant]

Labels intent: durable, architecture, priority:high

Problem

The implement agent step runs in an isolated /project/.agent-relay/step-artifacts/<step>/ context — its file ops don't land in REPO_DIR (/tmp/cloud-small-issue-<n>/cloud) that the deterministic preflight / open-pr steps share.

AgentWorkforce/cloud#1306 fix 3 (artifact restore) is a band-aid that copies the whole artifact tree back into REPO_DIR.

Root-cause fix

The workflow DSL (@agentworkforce/runtime) should let agent steps share the main sandbox FS at a configured cwd (REPO_DIR), so agent edits land directly in the checkout. This eliminates both:

• (a) the artifact-isolation that required the restore band-aid
• (b) the whole-tree restore that amplifies any over-edit into the PR diff (claude-2's catch)

Doubly-valuable: it removes a fragile band-aid AND reduces blast-radius of agent over-edits.

Acceptance

.step('implement', { agent, cwd: REPO_DIR, … }) (or equivalent) → agent's working dir is REPO_DIR → the restorePropagatedImplementationArtifacts block in personas/cloud-small-issue-codex/agent.ts becomes a no-op and can be removed in a follow-up.

Related

• AgentWorkforce/cloud#1306 (the band-aid this replaces)
• Filed as part of the proactive-agent E2E hardening pass (2026-05-28).