fix: stabilize alpine CI steps

- Fetch R version from Homebrew JSON API with jq instead of scraping
  the raw formula (was silently producing an empty version file that
  propagated to downstream steps).
- Replace grep -oP with grep -oE in the S3 listing step; BusyBox grep
  in the alpine image has no Perl-regex support.
- Add ephemeral-storage requests/limits to the Build step so the
  docker-cli apk extract doesn't fail with I/O errors under node
  disk pressure.

.crow/build.yaml

@@ -90,8 +90,8 @@ steps:
   - name: Get latest R version
     image: reg.devxy.io/docker.io/library/alpine:3.23
     commands:
-      - apk add -q --no-cache curl
-      - curl -s https://raw.githubusercontent.com/Homebrew/homebrew-core/master/Formula/r/r.rb | grep -o 'R-[0-9]*\.[0-9]*\.[0-9]*' | tr -d 'R-' | tr -d '"' | head -n 1 > r-version-to-build.txt
+      - apk add -q --no-cache curl jq
+      - curl -sf https://formulae.brew.sh/api/formula/r.json | jq -er '.versions.stable' > r-version-to-build.txt
       # - echo "4.1.3" > r-version-to-build.txt
       - cat r-version-to-build.txt
     backend_options:
@@ -114,7 +114,7 @@ steps:
       - |
           VERSION=$(cat r-version-to-build.txt)
           curl -s "https://s3.eu-central-003.backblazeb2.com/devxy-r-builds?prefix=${PLATFORM_ID}/" | \
-            grep -oP '<Key>[^<]+</Key>' | sed 's/<[^>]*>//g' | \
+            grep -oE '<Key>[^<]+</Key>' | sed 's/<[^>]*>//g' | \
             awk -v arch="${ARCH_ID}" -v ver="${VERSION}" \
               '$0 ~ arch && $0 ~ ver {print substr($NF, 3, 5)}' > r-version-s3.txt
       - cat r-version-s3.txt
@@ -142,9 +142,11 @@ steps:
           requests:
             memory: 200Mi
             cpu: 500m
+            ephemeral-storage: 2Gi
           limits:
             memory: 1000Mi
             cpu: 4000m
+            ephemeral-storage: 4Gi
         nodeSelector:
           kubernetes.io/arch: "${ARCH}"