Records an explicit decision about one issue and one PR. "linked" links them even without a reference,
"excluded" keeps them apart whatever references say, and "automatic" removes an earlier decision so that
references decide again. A decision outranks every automatic reference until it is changed.
(-- api-linter: core::0134::synonyms=disabled
aip.dev/not-precedent: Records a decision keyed by issue and PR; there is no resource to update. --)