sl0p: CSS-style 1/2/4-value shorthand for inner padding

`padding` now accepts:
  padding 1          -> all four sides
  padding 1 2        -> up/down = 1, left/right = 2
  padding 1 2 3 4    -> up=1 down=2 left=3 right=4

NOTE the 4-value order is UP DOWN LEFT RIGHT as requested, deliberately NOT
CSS's clockwise top-right-bottom-left. Documented on PanePadding and at the
parser, since the similarity to CSS invites the wrong assumption.

3 or 5 values are rejected with a message naming the accepted forms, rather
than being silently reinterpreted. Negative values clamp to 0.

ASPECT: only the 1-value form is aspect-corrected (left/right multiplied by
gap_aspect) so `padding 1` looks square on a non-square cell grid. The 2- and
4-value forms are literal: specifying axes separately means the caller is
already controlling horizontal size, and silently doubling it would surprise.

Style now carries a PanePadding {top,bottom,left,right} instead of an x/y
pair, which also collapses the reconfigure plumbing back to a single field
rather than growing another parameter per side.

to_kdl always emits the explicit 4-value form: emitting the 1-value form
would re-apply gap_aspect on the next read and silently double the padding
on every config round-trip.

Baselines held: zellij-utils 435/5, zellij-server 1421/30.

1 files changed, 1 insertions, 2 deletions

diff --git a/sl0ppij/zellij-client/src/web_client/server_listener.rs b/sl0ppij/zellij-client/src/web_client/server_listener.rs
index 8f80f4a..398c973 100644
--- a/sl0ppij/zellij-client/src/web_client/server_listener.rs
+++ b/sl0ppij/zellij-client/src/web_client/server_listener.rs
@@ -86,8 +86,7 @@ pub fn zellij_server_listener(
                             pane_title_alignment: config.ui.pane_frames.title_alignment,
                             pane_gap_x: config.ui.pane_frames.resolved_gap().0,
                             pane_gap_y: config.ui.pane_frames.resolved_gap().1,
-                            pane_padding_x: config.ui.pane_frames.resolved_padding().0,
-                            pane_padding_y: config.ui.pane_frames.resolved_padding().1,
+                            pane_padding: config.ui.pane_frames.resolved_padding(),
                         },
                     };