chore: commit remaining workspace updates

include AGENTS guidance updates, plan doc replacements, and utility script changes left in working tree

infra/scripts/app-down.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+set -euo pipefail
+
+SESSION_NAME="${SESSION_NAME:-social-dev}"
+
+echo "=== App Down ==="
+
+if ! tmux has-session -t "$SESSION_NAME" 2>/dev/null; then
+  echo "No tmux session '$SESSION_NAME' found."
+  exit 0
+fi
+
+echo "Stopping tmux session '$SESSION_NAME'..."
+
+tmux kill-session -t "$SESSION_NAME"
+
+echo "Session stopped and cleaned up."