Add key shortcut to toggle between Claude Code TUI and bash terminal

Feature Request

Add a keyboard shortcut that toggles between the Claude Code TUI and a bash terminal within the same tab/session.

Motivation

When working with multiple Claude Code sessions (6+), the current workflow requires two tabs per session: one for the Claude Code TUI and one for the user to do code review, run tests, add code comments, etc. This doubles the number of tabs needed.

A toggle shortcut would reduce this to one tab per session, making it much more manageable to work with many concurrent sessions.

Proposed Behavior

• A configurable keybinding (e.g. Ctrl+Z or similar) that suspends/backgrounds the Claude Code TUI and drops the user into their regular bash shell
• The user can do their work (review code, run tests, read files, add comments)
• Pressing the same shortcut or fg returns to the Claude Code TUI with full state preserved

Alternatives Considered

• Using tmux/screen splits within each tab — adds complexity and still takes screen real estate
• Ctrl+Z / fg already partially works for backgrounding processes, but a first-class integration would be smoother (preserving terminal state, status line, etc.)