Add Codex UI swarm dashboard

[areshand]

Summary

• pipe the orchestrator tmux pane into .multiagent/logs/orchestrator.log during launch
• pipe named subagent panes into .multiagent/logs/NAME.log on spawn and restore
• add bin/watch.sh, a Codex desktop-friendly terminal dashboard that summarizes agent status, blocked agents, DAG counts, blocked/failed DAG nodes, and the orchestrator log tail
• document the live dashboard workflow and cover it in the shell test suite

Validation

• bash -n launch.sh
• bash -n bin/subagent.sh
• bash -n bin/watch.sh
• bash tests/run.sh