Final omnibus updates

[iannevans]

(1) Numerous small wordsmithing changes.
(2) Split messenger and messenger_pdgid as agreed with Semantics.
(3) Moved the extension table summary table to the end of the section that defines the table entries.
(4) SIgnificant rewrites in section 6.

[bkhelifi]

All good for me, thanks a lot @iannevans

[mservillat]

Thanks for the many modifications and hard work to homogenise the text.

What is now section 6 is quite important to the discussion that will come after endorsement, so it should not be discarded. As it is now, it is truncated and limited to DataLink usages, while the concept of "specific tables" is also important to discuss further data discovery in a more generalised way. I am sure we can find a good formulation to express this solution in a paragraph. I however understand that the content of such a specialized table is not yet settled and requires more science cases. The proposition for a specialized response-function table as it is now could thus simply appear as an appendix. All this will then be discussed at the DM WG level.

About dataproduct_type = “measurements”, it is already planned to avoid its usage, so this paragraph can be removed. It is indeed written in the product-type vocabulary: "Because of its lack of specificity, this term should generally be avoided, and new, more precise terms should be introduced instead." (see https://www.ivoa.net/rdf/product-type/2026-01-15/product-type.html#measurements).