feat: git worktree isolation for write-capable rescue (write-race in shared checkout)

[axisrow]

Problem

/codex:rescue defaults to a write-capable Codex run (--write, agents/codex-rescue.md:36) operating directly in the caller's checkout via the workspace-write sandbox (plugins/codex/scripts/codex-companion.mjs:532). There is no writer isolation (no per-workspace writer lock, no worktree). When Codex runs — especially now that rescue defaults to background (PR #8) — concurrent writers to the same checkout can corrupt each other's work:

1. Concurrent uncommitted work — the user has staged/unstaged changes; Codex's edits interleave with them, making it hard to separate what Codex changed.
2. Parallel Claude + Codex — Claude Code edits the same files while background rescue is writing → race conditions, merge conflicts, overwritten uncommitted work.
3. No safe rollback — unwanted Codex changes require manual git checkout of individual files or git stash tricks.

How this surfaced

Found by a Codex adversarial review of PR #8 (rescue default → --background). PR #8 fixes the rescue hang (issue #7) but does not touch the --write default, so the race is pre-existing, not introduced by #8. Confirmed by code: gh pr diff 8 --name-only touches only commands/rescue.md, agents/codex-rescue.md, tests/commands.test.mjs — the --write default and workspace-write sandbox predate it. PR #8 merely makes an existing race reachable from one more code path.

Proposed solution

For write-capable rescue tasks, optionally run Codex in an isolated git worktree:

git worktree add .worktrees/codex-<timestamp> -b codex/<timestamp>

Then run the Codex task against the worktree path instead of the main working directory. After completion:

• Keep — generate a patch from the worktree and apply it to the main tree, or let the user merge the branch.
• Discard — git worktree remove + git branch -D.

Exposed as a --worktree flag on /codex:rescue, default for background write tasks (highest conflict risk). Must account for two related upstream issues:

• codex-rescue: forward intended worktree cwd to detached task openai/codex-plugin-cc#493 — rescue must forward the intended worktree cwd to the detached task (today it roots in the main checkout).
• [BUG] codex:codex-rescue hangs in worktrees when run_in_background is used openai/codex-plugin-cc#198 — a backgrounded rescue task must not have its worktree cleaned up before Codex finishes (early cleanup → hang). PR fix(rescue): default to --background, make Bash-tool timeout terminal (closes #7) #8's terminal-on-timeout already removes the polling trap that fed [BUG] codex:codex-rescue hangs in worktrees when run_in_background is used openai/codex-plugin-cc#198; verify the intersection.

Upstream

This is a fork-side tracking issue for openai#135, which has a ready closing PR: openai#137 (@peterdrier, feat: add --worktree flag for isolated write-capable rescue tasks, +496/−10, 12 tests in tests/worktree.test.mjs, OPEN 3 months, 0 human reviews). Plan: port openai#137 into this fork, adapt to openai#493/openai#198, open a fork PR.

Cross-links: openai#135 · openai#137 · openai#493 · openai#198 · fork#7 (hang, fixed by fork#8) · fork#8.

[axisrow]

Superseded by worktree leave-branch refactor (fork PR #12, merged). Rescue now uses leave-branch strategy instead of capture-then-remove, which avoids the shared-checkout write-race entirely.