The 'adding a language is two table entries plus its renderer' checklist
predates the `CodeSdkLanguage` union and now contradicts the mechanism
sentence beside it: following it literally leaves the union untouched, which
is exactly the excess-property error that sentence promises. It is three
parallel edits, in the note's Decision and Consequences and in the
`SDK_RENDERERS` JSDoc.
Two guard descriptions still claimed work the compiler took over. The
Decision's 'the drift this guards against' now names the `satisfies` pins and
leaves the guards their reachable case, a mounted runtime reporting a language
neither table knows; `resolveFlavor`'s JSDoc drops 'keeps the table coupled to
SDK_RENDERERS' for the same reason. The Consequences said a half-added
language 'cannot arise' for the runtime guards — it can, one PR later at the
consumer's integration point, and never on this base; the claim is now about
timing rather than impossibility.
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