build: use local go toolchain in release script

bible-local/08-build-release.md

@@ -61,6 +61,10 @@ Important limitation:
 - `scripts/release.sh` does not run `make build-all` for you
 - if you want Linux or additional macOS archives in the release directory, build them before running the script
 
+Toolchain note:
+- `scripts/release.sh` defaults `GOTOOLCHAIN=local` to use the already installed Go toolchain and avoid implicit network downloads during release builds
+- if you intentionally want another toolchain, pass it explicitly, for example `GOTOOLCHAIN=go1.24.0 ./scripts/release.sh`
+
 ## Run locally
 
 ```bash

scripts/release.sh

@@ -24,7 +24,9 @@ echo ""
 # Stable build env for this machine/toolchain
 export GOPATH="${GOPATH:-/tmp/go}"
 export GOCACHE="${GOCACHE:-/tmp/gocache}"
-export GOTOOLCHAIN="${GOTOOLCHAIN:-go1.22.12}"
+# Use the locally installed Go toolchain by default.
+# A pinned or auto-downloaded toolchain can still be requested via env override.
+export GOTOOLCHAIN="${GOTOOLCHAIN:-local}"
 mkdir -p "${GOPATH}" "${GOCACHE}"
 
 # Create release directory