feat: implement Mattermost proxy mirror with configuration and scripts for capturing traffic

scripts/mattermost-proxy/launch-mattermost.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+if [ -f "$SCRIPT_DIR/.env" ]; then
+  set -a
+  # shellcheck source=/dev/null
+  source "$SCRIPT_DIR/.env"
+  set +a
+fi
+
+APP_PATH="${MATTERMOST_APP_PATH:-/Applications/Mattermost.app}"
+APP_NAME="${MATTERMOST_APP_NAME:-Mattermost}"
+APP_BIN="${MATTERMOST_APP_BIN:-$APP_PATH/Contents/MacOS/Mattermost}"
+PROXY_HOST="${MATTERMOST_MIRROR_LISTEN_HOST:-127.0.0.1}"
+PROXY_PORT="${MATTERMOST_MIRROR_LISTEN_PORT:-8080}"
+LAUNCH_MODE="${MATTERMOST_MIRROR_LAUNCH_MODE:-open}"
+
+if [ "$LAUNCH_MODE" = "binary" ]; then
+  if [ ! -x "$APP_BIN" ]; then
+    echo "Mattermost app binary not found or not executable: $APP_BIN" >&2
+    echo "Set MATTERMOST_APP_BIN in scripts/mattermost-proxy/.env if needed." >&2
+    exit 1
+  fi
+
+  exec "$APP_BIN" --proxy-server="http://${PROXY_HOST}:${PROXY_PORT}"
+fi
+
+if [ ! -d "$APP_PATH" ]; then
+  echo "Mattermost app bundle not found: $APP_PATH" >&2
+  echo "Set MATTERMOST_APP_PATH in scripts/mattermost-proxy/.env if needed." >&2
+  exit 1
+fi
+
+# Prefer macOS LaunchServices over invoking the Electron binary directly.
+# Direct binary launch can crash sandboxed Electron apps with Mach rendezvous
+# errors because their expected app/container parent process is missing.
+exec open -n "$APP_PATH" --args --proxy-server="http://${PROXY_HOST}:${PROXY_PORT}"