chore(changeset): add the empty changeset the PR gate asks for (#4009)

`Check Changeset` fails any PR that adds no changeset. I had reasoned that a
comment-only diff needs none — but the gate's own error message states the right
escape hatch: "an empty changeset is fine for changes that release nothing".

So this is empty frontmatter, not a patch bump: giving @objectstack/rest a version
bump for a corrected doc comment would put a line in the CHANGELOG that consumers
cannot act on. There are already several precedents in .changeset for exactly this
shape (adr-0104-design-doc-only.md, adr-0110-draft-only.md, …).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CYbS3kS8xzsHNXFTzp4e2z

Author: claude

.changeset/packages-envelope-suite-comment.md

@@ -0,0 +1,14 @@
+---
+---
+
+Comment-only correction in `packages/rest/src/package-envelope.conformance.test.ts`
+(#3843 follow-up). Deliberately empty frontmatter: this releases nothing.
+
+Two sentences in that suite's header were written while #3841 was still undecided —
+"why #3841 still owns the vocabulary" (ADR-0112 has since closed it) and "this
+module needed MINTED codes" (true only of the four registered ones; the three
+generic conditions reuse the standard catalog). `package-routes.ts` already carried
+the corrected note; this was the test file missed beside it.
+
+No published behaviour, type, or wire shape changes, so there is nothing for a
+consumer to read in a CHANGELOG.