Plotnik now distinguishes failures by where they originate. Invalid queries, I/O failures, format limits reached by user-supplied data, and runtime capacity exhaustion remain Result or diagnostic paths. Once input has passed validation, missing artifacts, invalid indexes, inconsistent graph state, and impossible enum cases are treated as programmer errors. The change replaces silent fallbacks and debug-only checks with unconditional assertions carrying local context, and makes enum policy matches exhaustive so future variants cannot inherit behavior accidentally.

The same cleanup removes low-level unit tests that duplicate the retained snapshot, compile-diagnostic, fuzz, and integration suites. Their test-only helpers, module declarations, and dependencies are removed with them. Public query and bytecode formats remain unchanged.