fix: v0.10.3 no tmux right-click menus; close split panes

Right-clicking a pane opened tmux's menu, whose Split entries left a stray
pane next to Claude (and whose Kill entries could end it). Unbind the
right-click menus; add --unsplit and a palette entry that closes extra
panes and keeps Claude's. Closes #52

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WHRLCCdXYm41Qx5kNhehaP

bin/devdesk

@@ -15,7 +15,7 @@
 #
 # The web UI calls `devdesk attach --list | --repo NAME | --alerts | --investigate SESSION UID |
 # --upload SESSION FILE BYTES | --new NAME [PROJECT] [--worktree] | --rename OLD NEW | --end NAME |
-# --last-reply NAME | --existing NAME`
+# --last-reply NAME | --unsplit NAME | --existing NAME`
 # through ttyd; those print JSON.
 set -euo pipefail
 
@@ -182,6 +182,25 @@ dd_worktree_end() {
     fi
 }
 
+# --unsplit NAME (devdesk#52): close the extra panes a split left in the session's
+# windows. Each window keeps one pane: Claude's in the claude window, else the
+# first. Prints {ok, closed}.
+cmd_unsplit() {
+    [ $# -eq 1 ] || dd_die "usage: devdesk attach --unsplit NAME"
+    dd_valid_name "$1" || dd_die "invalid session name: $1"
+    { dd_server_up && dd_tmux has-session -t "=$1" 2>/dev/null; } || dd_die "session '$1' isn't running"
+    local win keep pane closed=0
+    while read -r win; do
+        keep=$(dd_tmux list-panes -t "=$1:$win" -F '#{pane_id} #{pane_start_command}' | awk '/devdesk-claude-run/ { print $1; exit }')
+        [ -n "$keep" ] || keep=$(dd_tmux list-panes -t "=$1:$win" -F '#{pane_id}' | head -n 1)
+        while read -r pane; do
+            [ "$pane" = "$keep" ] && continue
+            dd_tmux kill-pane -t "$pane" && closed=$((closed + 1))
+        done < <(dd_tmux list-panes -t "=$1:$win" -F '#{pane_id}')
+    done < <(dd_tmux list-windows -t "=$1" -F '#{window_index}')
+    jq -cMn --argjson c "$closed" '{ok: true, closed: $c}'
+}
+
 cmd_rename() {
     [ $# -eq 2 ] || dd_die "usage: devdesk rename OLD NEW"
     local old=$1 new=$2 running=0
@@ -366,7 +385,7 @@ cmd_attach() {
         dd_linger
         return
         ;;
-    --peek | --search | --last-reply)
+    --peek | --search | --last-reply | --unsplit)
         local action=${1#--}
         shift
         "cmd_${action//-/_}" "$@"