fix(zellij): remove whitespace on zellij layout file for Windows

[AmmoniumX]

Description

Simple fix: On Windows, if session has a space, such as claude c4e5832c2f, then when trying to open up a terminal using zellij, local layout-file inside zellij.lua becomes a string with a space, specifically config/zellij-layout-claude c9867a1555.kdl. Sidekick then seems to call zellij to initiate a terminal doing something like:

zellij --layout C:\Users\user\AppData\Local\nvim-data/sidekick/zellij-layout-claude c9867a1555.kdl

Which just causes the command to treat the last chunk as an extra argument, leading to the new zellij terminal to error with:

error: Found argument 'c9867a1555.kdl' which wasn't expected, or isn't valid in 
this context

The simplest fix (the one applied in this PR) is to just ensure session doesn't have whitespace by changing the format from %s %s to %s-%s

Screenshots

Issue screenshot: