bug: "duplicate session id" crash when a tmux pane exists in multiple sessions

[seflue]

Did you check docs and existing issues?

• I have read all the sidekick.nvim docs
• I have updated the plugin to the latest version before submitting this issue
• I have searched the existing issues of sidekick.nvim
• I have searched the existing issues of plugins related to this issue

Neovim version (nvim -v)

v0.11.6

Operating system/version

Linux (Manjaro)

Describe the bug

tmux list-panes -a returns one entry per session-pane combination. When a pane exists in multiple sessions (via link-window, session groups, etc.), M.panes() produces duplicate skid values because skid is derived from pane_pid. The assert in session/init.lua:142 then fails:

E5108: Error executing lua: .../sidekick/cli/session/init.lua:142: duplicate session id: tmux 1382785

I have a fix and will open a PR.

Steps To Reproduce

1. Start a supported CLI tool in any tmux session (e.g. claude)
2. Link that window into a second session:
   tmux link-window -s <source-session>:0 -t <target-session>
3. Open Neovim, toggle sidekick → crash

Expected Behavior

A linked pane is still one physical pane running one tool — sidekick should discover it once.

Repro

vim.env.LAZY_STDPATH = ".repro"
load(vim.fn.system("curl -s https://raw.githubusercontent.com/folke/lazy.nvim/main/bootstrap.lua"))()

require("lazy.minit").repro({
  spec = {
    {
      "folke/sidekick.nvim",
      opts = {
        cli = {
          mux = {
            backend = "tmux",
            enabled = true,
            create = "terminal",
          },
        },
      },
    },
  },
})
-- Before toggling sidekick, ensure a supported tool's tmux window
-- is linked into more than one session.

[franroa]

same issue here

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[seflue]

Bumping. The issue is not stale, just because nobody looked at it. I use the patch in the related PR every day and my workflow would break without it.

@folke What do I need to do to get the fix merged?