Fixed poetry-env plugin for Poetry >=2.0.0

Since version 2.0.0 poetry stopped using '[project.tool]' section in `pyproject.toml`. So the plugin didn't work for the newer poetry version.

With this change, the plugin will check for `pyproject.toml` and `poetry.lock` files to reliably check if it's a poetry project. In my testing, it worked with both poetry versions 1.8.5 and 2.0.1.

plugins/poetry-env/poetry-env.plugin.zsh

@@ -1,7 +1,7 @@
 _togglePoetryShell() {
   # Determine if currently in a Poetry-managed directory
   local in_poetry_dir=0
-  if [[ -f "$PWD/pyproject.toml" ]] && grep -q 'tool.poetry' "$PWD/pyproject.toml"; then
+  if [[ -f "$PWD/pyproject.toml" && -f "$PWD/poetry.lock" ]]; then
     in_poetry_dir=1
   fi