The absense of the hyphen really kade this one hard for me. I'll have to look out for omissions like that in later questions too just in case.
You're talking about the hyphen not appearing in the Word Bank where you select the words for the answer? Then you can mistake it for being an an, not an an-, and ignore it.
The absence of what hyphen?
Does 'te' not get a séimhiú? I'd have written 'ana-the'
It would get a séimhiú if you used the dialectal (Munster) ana. It doesn't with an, however, because of the DNTLS rule (t following an n)
So am I right in thinking every consonant gets a séimhiú after munster 'ana-' and none do after 'an-'? Is the DNTLS rule only about when two of those letters come together?
They all would in Munster, with ana- (which becomes an- before vowels). In Connacht, D and t and s wouldn't (not sure about l and n, honestly, which are lenited in speech but not in writing)