fix: delete codex sessions with backup

docs/codex-memory-isolation/README.md

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+# Codex Memory Isolation
+
+This folder tracks the Codbash fork work for Codex-only, project-isolated memory management.
+
+## Goal
+
+Build a local GUI workflow that turns noisy Codex conversation logs into isolated project memory:
+
+- Sessions remain grouped by repository or working directory, not by unreliable generated titles.
+- Each project owns its own `.codex-memory/` directory.
+- `.codex-memory/` is ignored by git by default.
+- OpenAI APIs generate titles, summaries, decisions, open threads, and embeddings.
+- Similar sessions are clustered inside a project first; cross-project similarity is only advisory.
+- Deletion remains a backed-up delete, using the Codex deletion path added in `034c481`.
+
+## Non-Goals
+
+- Managing Claude, Gemini, Cursor, or other agent histories.
+- Storing project memory in `~/.codex/memories` or any global memory folder.
+- Auto-merging memory across projects.
+- Sending sessions to non-configured external services.
+- Replacing Codex's native `resume` and `fork` commands.
+
+## Documents
+
+- `implementation-plan.md` - executable development plan for the next build stages.
+
+## Current Baseline
+
+Branch: `feat/codex-memory-isolation`
+
+Completed:
+
+- Codex session deletion now backs up before deleting.
+- Deletion removes Codex session JSONL, `history.jsonl`, `session_index.jsonl`, and attempts to remove the `state_5.sqlite` thread row.
+- Test coverage exists in `test/codex-delete.test.js`.
+
+## Desired Project Memory Layout
+
+```text
+<project>/.codex-memory/
+  manifest.json
+  sessions.index.json
+  clusters.json
+  context.md
+  decisions.md
+  open-threads.md
+  summaries/
+    <session-id>.md
+  embeddings/
+    <session-id>.json
+```
+
+## Default Safety Rules
+
+1. Add `.codex-memory/` to the project `.gitignore` during initialization.
+2. Keep raw Codex JSONL files out of project memory.
+3. Store summaries and embeddings per project, never globally.
+4. Before deleting Codex sessions, use the existing backed-up delete path.
+5. Treat cross-project similarity as a suggestion, not a merge operation.