docs(ci): say that the notes boundary is exclusive

Measured against goreleaser 2.15.3: a first milestone's notes start after the
first release rather than at it.

Claude-Session: https://claude.ai/code/session_01ShuAy8q8ZfPi8KHxwc8JpQ

docs/development/ci.md

@@ -315,6 +315,11 @@ level, so it reaches back to the first release there has ever been. A patch emit
 nothing, and an empty value leaves GoReleaser on the default that was already
 right for it.
 
+The boundary is exclusive, the way a changelog always is: the notes cover what
+landed *after* that tag. So the one release this shortchanges is the first
+milestone of its kind, whose notes start after the first release rather than at
+it. That is one merge, once, and it is not worth a special case.
+
 ### The npm credential
 
 `NPM_TOKEN` is a classic automation token. Those do not expire, which is the