Add a script/skill to prune dead projects from Codex CLI state

Problem

Codex CLI tracks workspace/project paths in a few places that grow over time and never get pruned when the underlying folder is deleted (worktrees, throwaway scratch dirs, removed repos, etc.):

1. ~/.codex/.codex-global-state.json:
   • active-workspace-roots — array of paths
   • electron-saved-workspace-roots — array of paths
   • project-order — array of paths
2. ~/.codex/sessions/<YYYY>/<MM>/<DD>/rollout-*.jsonl — each rollout's first line is a session_meta event with a cwd field pointing at the project the session was run from.
3. ~/.codex/archived_sessions/rollout-*.jsonl — same structure as sessions/.

There's no built-in way to garbage-collect any of these against on-disk reality.

Solution

A script (or skill) that:

1. Loads ~/.codex/.codex-global-state.json and walks each of the three arrays (active-workspace-roots, electron-saved-workspace-roots, project-order).
2. For each path, checks whether it still exists on disk (test -d).
3. For paths that no longer exist: drops them from the arrays.
4. (Optional, behind a flag like --prune-sessions) walks ~/.codex/sessions/**/rollout-*.jsonl and ~/.codex/archived_sessions/rollout-*.jsonl, reads the first JSONL line to extract payload.cwd, and deletes rollout files whose cwd no longer exists on disk.
5. Dry-run by default; require --apply to mutate.
6. Backs up ~/.codex/.codex-global-state.json before writing (there's already a .bak convention — append .bak with a timestamp or roll the existing one).
7. Prints a summary: dead entries per array, rollout files removed, total bytes reclaimed.

Nice-to-haves:

• --keep-sessions (default) vs --prune-sessions — keeping transcripts is the safer default since rollouts are useful history.
• --only <field> to target a single state-array (e.g. only fix project-order).
• Honor $CODEX_HOME instead of hardcoding ~/.codex.

Either a standalone bash/zsh script in this repo or an agent skill under skills/ would work — same shape as the analogous request on the Claude Code side (PaulRBerg/dot-claude#98).

Inspect the repository for existing scripts or skills, then use the issue's ~/.codex/.codex-global-state.json and sessions paths as the implementation targets. Start by confirming the state-array and rollout formats, including CODEX_HOME behavior. Done means a dry-run cleanup reports dead entries, --apply safely backs up and updates state, and session pruning remains opt-in.