Allow multiple CLI terminals per project

What variant of Codex are you using?

Version 26.217.1959 (669)

What feature would you like to see?

Description
Using Codex App on macOS, it’s currently possible to open only a single CLI terminal per project (via the top-right terminal button). This is limiting for common workflows where multiple long-running processes are needed in parallel (e.g., frontend dev server + backend API server).

Problem / Motivation
Many projects routinely require at least two concurrent terminal sessions:

• run a frontend dev server (npm run dev, pnpm dev, etc.)
• run a backend server / API (uvicorn, rails s, go run, etc.)
• optionally a third for logs, migrations, tests, tailing files, git ops, etc.

With only one terminal, you end up stopping/starting processes or context-switching to external terminals, which breaks flow.

Expected behavior
Within a single project, users can create multiple terminal sessions, ideally via:

• multiple tabs, and/or
• split panes (vertical/horizontal), and/or
• multiple terminal windows for the same project

Proposed UX (suggestion)

• Terminal button opens the “terminal panel”
• Add “+” to create a new terminal session
• Sessions appear as tabs or a sidebar list
• Optional: split current terminal into two panes
• Each session preserves its own working directory + process state

Acceptance criteria

• Users can open 2+ terminals within the same project
• Each terminal runs independently (one can run npm run dev while another runs python -m api)
• Switching terminals doesn’t kill running processes
• Basic lifecycle actions exist: create, close, rename (optional), restart (optional)

Notes / Edge cases

• Behavior on project close/reopen: restore sessions or reopen last used? (either is fine, but define it)
• Resource limits: cap number of terminals or warn if many are opened
• Keyboard shortcuts: new terminal, next/previous tab, split, close

Additional information

_No response_