Require both platform artifacts for releases

docs/remake-architecture-and-roadmap.md

@@ -1085,6 +1085,16 @@ do not mix mechanical moves with semantic changes.
    completed both platform artifact jobs and skipped tag-only promotion, accepting the runner/toolchain/cache/
    build/upload path and the non-tag authority boundary. Slice 4 is now active.
 
+   **Slice 4 implementation completed 2026-08-03; hosted acceptance pending:** tag promotion now requires both
+   successful platform jobs and downloads their already-built artifacts into separate directories. The helper
+   binds both archives to the same clean tag commit/RID, verifies their external hashes, compares external build
+   metadata and payload ledgers with the copies inside each archive, requires Linux's dynamic smoke and Windows's
+   AMD64/ABI/import report, and generates combined release checksums. Creation and retry expose exactly three
+   public assets—Linux archive, Windows archive, and `RELEASE-SHA256SUMS`—while unexpected assets, release
+   mismatches, and same-name/different-size collisions fail without mutation. Synthetic paired-artifact,
+   creation/resume/refusal, and workflow-dependency tests pass. The next gate is a hosted develop run with both
+   builds green and promotion skipped; only after that proof may the user deliberately select a future tag.
+
    **Completion gate:** one deliberately selected future tag produces a single Gitea release containing the
    Linux `.tar.gz`, Windows `.zip`, and combined archive checksums; both archives bind to the tag commit, Linux
    retains its dynamic packaged smoke, Windows passes all structural PE/payload gates, and neither platform job