build(make): add lint target and run it as part of make test

`make lint` runs ruff on src and tests directly on the host, using the
same invocation as the lint-python workflow so local and CI agree. The
script fails with a clear install hint when ruff is not on PATH.

`make test` now depends on `lint`, so linting runs before the container
images are built.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/lint/python.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+echo "============================================================"
+echo ">>> Running RUFF lint on src and tests (local, no container)"
+echo "============================================================"
+
+if ! command -v ruff >/dev/null 2>&1; then
+  echo "ruff is not installed or not on PATH." >&2
+  echo "Install it with: pip install ruff" >&2
+  exit 127
+fi
+
+ruff --version
+ruff check src tests