sl0p: serialise the pane status bar for resurrection

The status bar survived detach/reattach (it lives on Grid) but not a
serialise/restore cycle, so a resurrected pane came back blank.

It now travels the whole per-pane serialisation pipeline, mirroring the fork's
existing default_fg/default_bg: pane -> PaneLayoutMetadata ->
PaneLayoutManifest -> TiledPaneLayout -> a status_bar property in the serialised
KDL, then back through the normal layout parser and applied by LayoutApplier
when the pane is recreated.

The sanitiser moved from grid.rs into zellij-utils so both entry points share
one definition. That matters: a layout file on disk is no more trustworthy than
the escape sequence that wrote it -- it may have been hand-edited, or copied from
somewhere else -- so restored text is stripped and length-capped on the way in
just like the OSC payload was.

Verified end to end rather than by unit test alone: set the bar, waited for a
serialisation pass, confirmed status_bar="..." in session-layout.kdl, killed the
session until list-sessions reported EXITED, then attached and watched it come
back from disk. The earlier attempt only proved detach/reattach because Quit had
left the session alive.

0 files changed, 0 insertions, 0 deletions