- mix.exs: @version 0.2.0 -> 0.3.0
- README.md: the install pin goes to ~> 0.3
- CHANGELOG.md: assembles the 0.3.0 section from the one fragment
- changelog.d/sd-wj1.md: the promoted fragment deleted

MINOR under 0.x, not a patch: the release changes what
`Compatibility.breaks/2` reports. A declaration field's `one_of` is a
completion hint and never a break, so `{:group_added, name}` is gone,
and a record field going required -> optional is a break in its place,
`{:made_optional, name}`. A caller matching on the removed tuple stops
matching. The release also lets an entry's `type`, and a `list` entry's
`item_type`, name a declaration. Both arms are recorded in the
sd-ADR-0001 amendment accepted on the operator's campaign-034 ruling.

The section is dated 2026-09-06, the local date on the machine cutting
the prep, per the convention release.md records. The fragment's bullets
are carried over byte for byte, and the lead paragraph is the only prose
written at release time.

Cut, not published: the tag, the GitHub release and the Hex publish are
the operator's.

Refs: sd-ql2