fix(templates): carry the optional Owners section into the shape starters

ef76a04a fixed only the standard's own CODEOWNERS template; the three shape starters (docs/lab/paper) still shipped the required catch-all plus the header recommending the toggle that arms it. A stamped project would recreate the Renovate CODEOWNERS deadlock on day one. All three now carry ^[Owners] and the load-bearing-caret warning.

Last of the stacked chain; merge the three MRs below it first.