fix: use GitHub API to find Roc tarball URL (inconsistent naming) and fix default version to 0.0.0-alpha1

scripts/download-roc.sh

@@ -11,16 +11,40 @@ case "$TARGETARCH" in
   *)      echo "Unsupported architecture: $TARGETARCH" >&2; exit 1 ;;
 esac
 
-TARBALL="roc-linux_${ROC_ARCH}-${ROC_VERSION}.tar.gz"
-URL="https://github.com/roc-lang/roc/releases/download/${ROC_VERSION}/${TARBALL}"
+# Use the GitHub API to find the correct asset URL for this version + arch.
+# We can't construct the URL from the version string because Roc release
+# tarball naming is inconsistent across releases (e.g. 0.0.0-alpha1 uses
+# "roc-linux_x86_64-0-alpha1.tar.gz" while alpha4-rolling uses
+# "roc-linux_x86_64-alpha4-rolling.tar.gz").
+# awk is used instead of jq/python because neither is guaranteed in slim images.
+API_URL="https://api.github.com/repos/roc-lang/roc/releases/tags/${ROC_VERSION}"
+echo "Looking up release ${ROC_VERSION} via GitHub API..."
+curl -fsSL "$API_URL" -o /tmp/gh-release.json
+
+ASSET_URL=$(awk -v arch="roc-linux_${ROC_ARCH}" '
+  /"browser_download_url"/ {
+    url = $2
+    gsub(/[",]/, "", url)
+    if (index(url, arch) > 0 && url ~ /\.tar\.gz$/) {
+      print url
+      exit
+    }
+  }
+' /tmp/gh-release.json)
+rm -f /tmp/gh-release.json
+
+if [ -z "$ASSET_URL" ]; then
+  echo "ERROR: No linux ${ROC_ARCH} tarball found for release ${ROC_VERSION}" >&2
+  exit 1
+fi
 
 echo "Downloading Roc ${ROC_VERSION} for ${ROC_ARCH}..."
-curl -fsSL "$URL" -o /tmp/roc.tar.gz
+curl -fsSL "$ASSET_URL" -o /tmp/roc.tar.gz
 
 echo "Extracting..."
 tar -xzf /tmp/roc.tar.gz -C /tmp/
 
-# The tarball contains a single directory with an unpredictable nightly name
+# The tarball contains a single directory with an unpredictable name
 # e.g. roc_nightly-linux_x86_64-2025-09-09-d73ea109/
 EXTRACTED_DIR=$(find /tmp -maxdepth 1 -type d -name "roc_*" | head -1)
 if [ -z "$EXTRACTED_DIR" ]; then