feat(fleet): add durable tmux fleet poc

packages/mosaic/framework/tools/fleet/start-agent-session.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+AGENT_NAME=${1:-${MOSAIC_AGENT_NAME:-}}
+MOSAIC_TMUX_SOCKET=${MOSAIC_TMUX_SOCKET:-mosaic-factory}
+MOSAIC_AGENT_RUNTIME=${MOSAIC_AGENT_RUNTIME:-pi}
+MOSAIC_AGENT_WORKDIR=${MOSAIC_AGENT_WORKDIR:-$HOME}
+MOSAIC_AGENT_COMMAND=${MOSAIC_AGENT_COMMAND:-}
+
+if [ -z "$AGENT_NAME" ]; then
+  echo "ERROR: agent name argument or MOSAIC_AGENT_NAME is required" >&2
+  exit 64
+fi
+
+if ! command -v tmux >/dev/null 2>&1; then
+  echo "ERROR: tmux is required" >&2
+  exit 69
+fi
+
+if tmux -L "$MOSAIC_TMUX_SOCKET" has-session -t "=${AGENT_NAME}:0.0" 2>/dev/null; then
+  echo "Mosaic agent session already running: $AGENT_NAME on socket $MOSAIC_TMUX_SOCKET"
+  exit 0
+fi
+
+if [ -z "$MOSAIC_AGENT_COMMAND" ]; then
+  MOSAIC_AGENT_COMMAND="mosaic yolo $MOSAIC_AGENT_RUNTIME"
+fi
+
+mkdir -p "$MOSAIC_AGENT_WORKDIR"
+exec tmux -L "$MOSAIC_TMUX_SOCKET" new-session -d -s "$AGENT_NAME" -c "$MOSAIC_AGENT_WORKDIR" "$MOSAIC_AGENT_COMMAND"