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

share/tmux.conf

@@ -8,7 +8,13 @@ set -s set-clipboard on                # tmux copy-mode -> OSC 52 -> browser cli
 set -s default-terminal "tmux-256color"
 set -s terminal-features[90] "xterm-256color:RGB"  # fixed index: re-sourcing must not append
 set -g history-limit 50000
-set -g mouse on                        # wheel scrolls history; Shift+drag selects natively
+set -g mouse on                        # wheel scrolls history; a drag selects in the browser (devdesk#51)
+# No right-click menus (devdesk#52): one stray click on them splits a pane or
+# kills a window (Claude's). Splits and kills stay on the keyboard (^b % ^b x).
+unbind -n MouseDown3Pane
+unbind -n M-MouseDown3Pane
+unbind -n MouseDown3Status
+unbind -n MouseDown3StatusLeft
 set -g allow-passthrough off       # output may not bypass tmux (title/clipboard spoofing)
 set -g renumber-windows on