Move scenario sync script to top-level scripts (#2788)

Same idea as https://github.com/astral-sh/uv/pull/2787

scripts/sync_scenarios.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+#
+# Sync test scenarios with the pinned version of packse.
+#
+# Usage:
+#
+#   Install the pinned packse version in a temporary virtual environment, fetch scenarios, and regenerate test cases and snapshots:
+#
+#       $ ./scripts/scenarios/sync.sh
+#
+#   Additional arguments are passed to `./scripts/scenarios/generate.py`, for example:
+#
+#       $ ./scripts/scenarios/sync.sh --verbose --no-snapshot-update
+#
+#   For development purposes, the `./scripts/scenarios/generate.py` script can be used directly to generate
+#   test cases from a local set of scenarios.
+
+set -eu
+
+script_root="$(realpath "$(dirname "$0")")"
+
+
+cd "$script_root/scenarios"
+echo "Setting up a temporary environment..."
+uv venv
+
+source ".venv/bin/activate"
+uv pip install -r requirements.txt --refresh-package packse
+
+echo "Fetching packse scenarios..."
+packse fetch --dest "$script_root/scenarios/.downloads" --force
+
+python "$script_root/scenarios/generate.py" "$script_root/scenarios/.downloads" "$@"
+
+# Cleanup
+rm -r "$script_root/scenarios/.downloads"