DL-410

A PR is linked to its issue by an explicit CreatePullRequestRequest.issue coordinate (forge + repo + number), shape-checked but never tracker-read at create and written in one transaction with the DL-055 row and the PR row; without one, every GitHub closingIssuesReferences entry is a link, recomputed on each hydrate. Ingestion never removes or downgrades an explicit link, and a PR whose explicit targets are all off the board (including every Linear target, until Linear issues are board rows) falls back to its closing references at read time

Status: Active (Matt, 2026-10-05)

Record: ../../server/compass-issue-model-pr-linkage-amendment/design.md#3-precedence