E.5.1:5.1 - Four placement decisions

Actual governed use	Placement and first action
E.8 H-1/H-6/H-9 govern this edition’s Markdown pattern headings: level-2 `##`, the identifier/title separator `-`, and `### <PatternId>:End`.	Keep those necessary syntax fragments in E.8. The author can write/check the heading and sentinel; “the reference heading mark” would lose the condition. The rule is about this publication form, not the ontology of the described System.
An unrelated abstract System definition requires a container-build command.	Move the command and its operational prerequisites to Tooling. Recover the System definition independently of that implementation.
A runnable program demonstrates a conceptual method.	Keep the program in its teaching/Tooling source and cite its conceptual role from Core. Calling it a grammar example does not change its role.
A Euclidean construction expression supplies a reasoning step under the subject Method.	Keep the expression where its meaning, construction operation and prerequisites are supplied under E.5.2. Its operative role is not reduced to illustration; compared expressions retain their mapping duty.