Changelog entries between two versions of a package (upgrade intelligence)

Given a package and a from/to version, returns the ordered release entries in the half-open range (from, to] — from exclusive (you have it), to inclusive — with summaries, breaking-change verdicts (#1696), and migration notes. One call instead of N changelog pages.

Reads already-ingested releases only (no live fetch). Resolution is read-only: an exact catalog source-slug match, then a non-materializing GitHub owner/repo coordinate match. An unresolvable package returns status: "unknown" with HTTP 200 — a valid answer, not an error; npm/PyPI names absent from the catalog resolve to unknown until the name→source map (#1345) lands. Wide ranges are truncated to a token budget (newest entries kept), flagged via truncated.