Then build a session freezer that snapshots a running tmux session and
rebuilds it later.

libtmux drives a real tmux server from code. It gives you objects for the
server, its sessions, windows and panes. Documentation for every language
is at https://libtmux.org/en/.

Language:   Rust
Package:    libtmux (crates.io)
Repository: https://github.com/libtmux/libtmux-rs

Read these before writing code:
- https://libtmux.org/en/rs/latest/llms.txt
  every page for Rust, as a list
- https://libtmux.org/en/rs/latest/docs.json
  the same list with headings, as JSON
- https://libtmux.org/en/rs/latest/reference/
  the Rust API reference
- https://docs.rs/libtmux
  Rust reference on docs.rs
If you cannot fetch URLs, clone the repository above and read its README
and examples instead, or ask me to paste those pages in.

Set up first:
1. Report the tmux version with `tmux -V`. libtmux drives a real tmux, so
   nothing below works without one. Stop and tell me if it is missing.
2. If this directory is not a Rust project yet, start one:
       cargo init
   Skip this in a project that already exists, and match what is here.
3. Add the dependency. libtmux has no stable release. 0.1.0-alpha.15 is the
   newest prerelease on crates.io, and the command below names it because the
   resolver skips prereleases otherwise.
       cargo add libtmux@0.1.0-alpha.15
   Check https://crates.io/crates/libtmux for a newer version, and prefer a
   stable release over this one if there now is any.
4. Write the smallest program that proves the install works: connect to a
   tmux server, create a session, confirm it is there, then kill it. Give
   that server a socket of its own rather than using the default one, so
   this never touches a tmux I am already running. Run it, and show me the
   output and the files you added.

Rules for everything below:
- Use the reference above rather than guessing names. The ten libtmux
  ports do not share spellings, and a name from another language will look
  plausible and not exist.
- If the reference does not have something you expected, say so instead of
  writing a call that does not exist.
- Follow the conventions already in this repository.

Session freezer

What it does:
- Reads a live session and writes a workspace file describing it: windows,
  their names and layouts, each pane's working directory and running command.
- Rebuilds that session from the file, on this machine or another one.
- Round-trips. Freezing a session, rebuilding it, and freezing it again gives
  the same file. Show me that this holds rather than asserting it.

Constraints:
- Record the working directory each pane is actually in, not the directory the
  session started in.
- A running command and a shell sitting at a prompt are different states. Do
  not write a shell prompt out as if it were a command to re-run.
- Say what you deliberately do not capture. Scrollback and program state do not
  survive this, and a reader should know that before trusting it.

Anchor it in these pages:
- https://libtmux.org/en/tmux/concepts/workspaces/           workspaces
- https://libtmux.org/en/tmux/concepts/queries/              queries
- https://libtmux.org/en/tmux/examples/workspace-from-file/  workspace from file