docs: plan durable tmux fleet install (#557)

packages/mosaic/framework/systemd/user/test-fleet-units.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR=$(cd -- "$(dirname -- "$0")" && pwd)
+HOLDER="$SCRIPT_DIR/mosaic-tmux-holder.service"
+AGENT="$SCRIPT_DIR/mosaic-agent@.service"
+
+fail() {
+  echo "FAIL: $*" >&2
+  exit 1
+}
+
+[ -f "$HOLDER" ] || fail "missing mosaic-tmux-holder.service"
+[ -f "$AGENT" ] || fail "missing mosaic-agent@.service"
+
+grep -qF 'ExecStart=' "$HOLDER" || fail "holder has no ExecStart"
+grep -qF 'tmux -L' "$HOLDER" || fail "holder does not use named tmux socket"
+grep -qF '_holder' "$HOLDER" || fail "holder session is not explicit"
+grep -qF 'Requires=mosaic-tmux-holder.service' "$AGENT" || fail "agent does not require holder"
+grep -qF 'start-agent-session.sh' "$AGENT" || fail "agent unit does not call start-agent-session.sh"
+grep -qF 'kill-session -t "=%i"' "$AGENT" || fail "agent stop does not exact-match its session"
+
+if command -v systemd-analyze >/dev/null 2>&1; then
+  systemd-analyze verify --user "$HOLDER" "$AGENT" >/tmp/mosaic-fleet-systemd-verify.log 2>&1 || {
+    cat /tmp/mosaic-fleet-systemd-verify.log >&2
+    fail "systemd-analyze verify failed"
+  }
+fi
+
+echo "ok - fleet systemd unit templates"