Fix TID validation #4

TID format validator was rejecting valid TIDs like 3m3zm7eurxk26.

It seems like syntax format assumed in the file is wrong, so I amended it to use https://atproto.com/specs/tid#tid-syntax. In particular, see the "reference regex" in the spec, which is /^[234567abcdefghij][234567abcdefghijklmnopqrstuvwxyz]{12}$/ and doesn't match old code.

This is vibecoded so be cautious (though both Claude and ChatGPT seem happy with the result). I've also asked Claude to cross-check the new tests against atproto/packages/syntax/src/tid.ts.