[cloud-push] Codex adapter: conversation continuity across push/pull

[Zeus-Deus]

Context

PR #15 added bidirectional Claude conversation sync. Codex is the next priority for agent parity (per user, Codex + Pi before Gemini).

Today: pushing a workspace with an active Codex pane → Codex launches on the remote with a fresh conversation. We strip args and run bare `codex` (see `src-tauri/src/terminal/daemon_backed.rs` around line 488).

What needs research first

Before writing code, document the answers to these in a comment on this issue:

1. Where does Codex store conversation history? (`/.codex/`, `/.config/openai-codex/`, or somewhere else?)
2. What's the file/path layout? Per-project files like Claude, or a single DB like OpenCode, or something else?
3. What's the resume command? `codex --resume `, `codex chat resume`, or interactive-only?
4. How to capture the session id? Hooks like Claude, plugin like OpenCode, output scanning, or file watching?

Look at:

• https://github.com/openai/codex (or wherever the CLI source lives)
• `codex --help` output
• The actual files Codex creates locally when you run a session

Acceptance criteria

• Push workspace with a Codex pane → conversation continues on remote
• Pull back → conversation continues on laptop
• 3+ push/pull cycles preserve full history

Implementation pattern

Mirror what PR #15 did for Claude (commit `495f62f`):

1. Helper in `src-tauri/src/commands/hosts.rs` to rsync (or extract+merge if DB-shaped) the per-workspace Codex session data between laptop and remote. Reuse the path-encoding pattern from `crate::ssh::claude_project_dir_name` if Codex's layout is similar
2. Register a Codex adapter in `src-tauri/src/session_adapters.rs` — currently only `claude-code` exists (see line 115–128)
3. Session-id capture via whatever Codex provides — emit to `adapter_captures["codex_session_id"]` on the active `TerminalSessionSnapshot`
4. Remote-relaunch branch in `src-tauri/src/terminal/daemon_backed.rs` (around line 488–573) that builds the correct `codex --resume` invocation

References

• Claude pattern (template to follow): commit `495f62f` in PR feat: push workspace to remote SSH host with Claude conversation sync #15
• Existing adapter trait: `src-tauri/src/session_adapters.rs`
• Encoding helper: `crate::ssh::claude_project_dir_name` (only useful if Codex also uses cwd-encoded directories)

Out of scope

• OpenCode (issue [cloud-push] OpenCode conversation sync via SQLite extract+merge #16), Pi, Gemini — separate issues
• Refactoring Claude's path

Estimate

If Codex is per-cwd file-based (like Claude): ~2 hours.
If Codex is DB-based (like OpenCode): ~half-day.
Research first, estimate after.