fix(skills): auto-run /sprint-start in team tabs

Pass "claude /sprint-start" as the initial tmux command so each team
tab loads its briefing and spawns agents automatically — no manual
step needed after tabs open.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/skills/sprint-start/scripts/start-sprint.sh

@@ -58,7 +58,7 @@ for team in $TEAMS; do
     fi
   fi
 
-  ptyxis --tab -d "$WDIR" -x 'tmux new-session \; send-keys claude Enter'
+  ptyxis --tab -d "$WDIR" -x 'tmux new-session \; send-keys "claude /sprint-start" Enter'
   sleep 0.3
 done