Distill an entry whose range is a list of per-PR ranges

[sameera]

/nxs.distill drains an entry whose range is a list: the diff is the aggregation of the per-PR merge-anchored diffs (never one spanning base...head, which would swallow interleaved epics), with repo-qualified anchors, provenance, and drain-SLO reporting working across N ranges per repo.

Meta

• feature: docs/features/multi-repo-workspaces
• estimate: M
• candidate stories: Per-PR diff aggregation from the range list; Anchors and provenance over N ranges; Drain-SLO reporting for multi-range entries
• source: decomposition of "Refactor multi-repo workspaces around PR-driven delivery (hub-born queue)" (2026-07-20)
• migrated: 2026-08-01, from the per-feature backlog file retired by Backlog Stubs Become GitHub Issues #185