fix: reuse goose2 vite server on port conflict (#8722)

Signed-off-by: Taylor Ho <taylorkmho@gmail.com>
Signed-off-by: Douwe Osinga <douwe@squareup.com>
Co-authored-by: Douwe Osinga <douwe@squareup.com>

ui/goose2/scripts/start-dev-vite.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+VITE_PORT="${1:-${VITE_PORT:-}}"
+if [[ -z "${VITE_PORT}" ]]; then
+    echo "VITE_PORT is required" >&2
+    exit 1
+fi
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_DIR="$(cd "${SCRIPT_DIR}/.." && pwd)"
+
+PID=$(lsof -ti :"${VITE_PORT}" 2>/dev/null | head -1 || true)
+if [[ -n "${PID}" ]]; then
+    PROC_ARGS="$(ps -p "${PID}" -o args= 2>/dev/null || true)"
+    PROC_CWD="$(lsof -a -p "${PID}" -d cwd -Fn 2>/dev/null | sed -n 's/^n//p' | head -1)"
+    if [[ "${PROC_CWD}" == "${PROJECT_DIR}" && "${PROC_ARGS}" == *"--port ${VITE_PORT} --strictPort"* ]]; then
+        echo "Reusing existing Goose2 Vite dev server on port ${VITE_PORT} (PID ${PID})"
+        exit 0
+    fi
+
+    PROC_NAME="$(ps -p "${PID}" -o comm= 2>/dev/null || true)"
+    echo "Port ${VITE_PORT} is already in use by '${PROC_NAME}' (PID ${PID})." >&2
+    echo "Run 'just goose2 kill' if it is a stale Goose2 dev server, or rerun with VITE_PORT=<free-port> just goose2 dev." >&2
+    exit 1
+fi
+
+cd "${PROJECT_DIR}"
+exec pnpm exec vite --port "${VITE_PORT}" --strictPort