Shell installer (canpy-installer.sh, curl | sh) #42

Add an opt-in integration test that provisions a real Neo4j and asserts the
pushed graph, exercised only when a container runtime is available.

Scope:

• test/test_neo4j_bolt.py, gated by RUN_CONTAINER_TESTS=1
• assert full push, idempotent re-push, vanished-declaration cleanup, full-run orphan prune