docs: fix stale README examples and execute them in CI

[rahlk]

The README quick-start calls analysis.get_method_body(...) and the Neo4j example calls get_all_classes() — neither method exists on the facades (get_method_bodies is Python-only; the real method is get_classes()). Nothing executes README examples, so drift goes unnoticed.

Scope

• Fix the stale examples.
• Add a test that extracts and executes README code blocks against the bundled sample apps, wired into PR CI.

Part of #193. Branch: chore/issue-<n>.