Then build a tmux session switcher.

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:   C#
Package:    LibTmux (NuGet)
Repository: https://github.com/libtmux/libtmux-dotnet

Read these before writing code:
- https://libtmux.org/en/csharp/latest/llms.txt
  every page for C#, as a list
- https://libtmux.org/en/csharp/latest/docs.json
  the same list with headings, as JSON
- https://libtmux.org/en/csharp/latest/reference/
  the C# API reference
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 C# project yet, start one:
       dotnet new console
   Skip this in a project that already exists, and match what is here.
3. Add the dependency. LibTmux has no stable release. 0.0.0-alpha.21 is the
   newest prerelease on NuGet, and the command below names it because the
   resolver skips prereleases otherwise.
       dotnet add package LibTmux --version 0.0.0-alpha.21
   Check https://www.nuget.org/packages/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 switcher

What it does:
- Lists every session on the server with its windows, and shows what each
  window's active pane is running, so the list says something more useful than
  a set of names.
- Filters as I type and attaches to, or switches the client to, what I pick.
- Works both from outside tmux and from inside it. Those need different calls,
  and getting the inside case wrong is the usual bug here: attaching from
  within a session nests one client inside another.

Constraints:
- Read the live server every time. Do not cache a session list between runs.
- Handle there being no server running at all, which is the first-run case.
- Fetch the listing in as few round trips as the API allows and say how many it
  costs. One call per pane is the slow shape this should avoid.
- Keep it to one file I can read in a sitting.

Anchor it in these pages:
- https://libtmux.org/en/tmux/concepts/queries/
  queries
- https://libtmux.org/en/tmux/guides/querying-and-filtering/
  querying and filtering
- https://libtmux.org/en/tmux/guides/attaching-to-tmux/
  attaching to tmux