Use the host target for source-built release tools

docs/release.md

@@ -193,10 +193,16 @@ immutable version from its tag:
 ```sh
 git fetch origin "refs/tags/vX.Y.Z:refs/tags/vX.Y.Z"
 git checkout --detach "vX.Y.Z"
-GOTOOLCHAIN=local go mod download
-mkdir -p .releasekit/bin
-GOTOOLCHAIN=local GOPROXY=off GOSUMDB=off go build -o .releasekit/bin/releasekit ./cmd/releasekit
-.releasekit/bin/releasekit deliver "vX.Y.Z"
+(
+  set -e
+  releasekit_host_os=$(GOTOOLCHAIN=local go env GOHOSTOS)
+  releasekit_host_arch=$(GOTOOLCHAIN=local go env GOHOSTARCH)
+  export GOOS="$releasekit_host_os" GOARCH="$releasekit_host_arch"
+  GOTOOLCHAIN=local go mod download
+  mkdir -p .releasekit/bin
+  GOTOOLCHAIN=local GOPROXY=off GOSUMDB=off go build -o .releasekit/bin/releasekit ./cmd/releasekit
+  .releasekit/bin/releasekit deliver "vX.Y.Z"
+)
 ```
 
 For an older tag whose CLI predates `token_file`, supply the token through its

docs/roadmap/implementation.md

@@ -70,6 +70,8 @@ checks in Stage 6.
 
 ## Stage 3: Normalize source-built launchers
 
+**Completed.**
+
 1. Apply the same recipe in the [maintainer launcher](../../scripts/release)
    before building and executing ReleaseKit. Prefix the two queries with
    `GOTOOLCHAIN=local` to match its existing build. Preserve usage checking,