The SEVERITY table's stated rationale no longer covers DUPLICATE_TAXON_NAME

[realmarcin]

Found reviewing PR #332. Documentation accuracy.

src/communitymech/network/auditor.py explains the error tier as:

Everything at error level names something that is not there: an interaction citing a taxon the record does not list, a causal edge or discussion anchor pointing at an interaction that does not exist, an id that disagrees with the taxonomy entry it refers to.

DUPLICATE_TAXON_NAME is none of those three — it is a record naming one thing twice, not naming something absent. The comment is the reference a future contributor uses to decide a new type's severity, so leaving it incomplete invites a wrong call.

Same omission in .github/workflows/network-quality.yml: the note string for the errors job summary and PR comment enumerates the gating categories for curators, and now does not cover duplicates.