sl0p: configurable pane title alignment

Adds `ui { pane_frames { title_alignment "left"|"center"|"right" } }`.

Full-frame panes previously hardcoded the title flush left, while frameless
panes (pane_frame_style "titles") already centered it via
compose_bracketed_title. This brings full frames up to parity and makes the
position configurable.

Implementation notes:
- The value rides on `Style`, which is already threaded to FrameParams, so no
  new plumbing through Tab/PaneContentsAndUi was needed.
- It is deliberately NOT round-tripped over the plugin protobuf boundary:
  plugins have no use for frame title alignment and adding a proto field
  would force regenerating the committed prost assets in assets/prost/.
- Left keeps the original code path untouched, so default configs render
  exactly as before.
- The geometry loop clamps the title start against the right-side indicators
  and breaks on `>=` rather than `==`, so a mis-clamped segment cannot spin.

Tests: alignment ordering, frame width preservation across widths, and
narrow-pane safety (cols 1..24 must not panic or corrupt width).

1 files changed, 1 insertions, 0 deletions

diff --git a/zellij-client/src/web_client/server_listener.rs b/zellij-client/src/web_client/server_listener.rs
index c66a1286..5d753435 100644
--- a/zellij-client/src/web_client/server_listener.rs
+++ b/zellij-client/src/web_client/server_listener.rs
@@ -83,6 +83,7 @@ pub fn zellij_server_listener(
                             colors: palette,
                             rounded_corners: config.ui.pane_frames.rounded_corners,
                             hide_session_name: config.ui.pane_frames.hide_session_name,
+                            pane_title_alignment: config.ui.pane_frames.title_alignment,
                         },
                     };