ci: bump bincraft to 4.2.1 and scope multi-R loops to versioned R dirs

- Pin bincraft v4.2.0 -> v4.2.1 (per-minor archive.rds/index fix) across the
  process-updates, weekly-rebuild and archive workflows.
- Restrict the per-R-minor build and index loops to /opt/R/[0-9]* so the
  `current` symlink dir is not treated as a distinct minor (avoids double-
  building a minor and writing a bogus contrib/current/ index slot).

.crow/build-all-versions-arm64.yaml

@@ -85,7 +85,7 @@ steps:
       - $XVFB $XVFB_ARGS -n $SPLIT_INDEX -- /opt/R/$R_VERSION/bin/Rscript local/build-all.R $SPLIT_INTO $SPLIT_INDEX $NCPUS 2>&1
       - |
         PRIMARY_MINOR=$(echo "$R_VERSION" | cut -d. -f1-2)
-        for RBIN in /opt/R/*/bin/R; do
+        for RBIN in /opt/R/[0-9]*/bin/R; do
           RV=$(basename "$(dirname "$(dirname "$RBIN")")")
           RMINOR=$(echo "$RV" | cut -d. -f1-2)
           [ "$RMINOR" = "$PRIMARY_MINOR" ] && continue
@@ -134,7 +134,7 @@ steps:
       - |
         CODENAME=$(/opt/R/$R_VERSION/bin/Rscript -e "cat(bincraft::set_codename(NULL))")
         /opt/R/$R_VERSION/bin/R -q -e "bincraft::upload_package_index(codename = '$CODENAME', s3_endpoint = 'https://s3.eu-central-003.backblazeb2.com', s3_region = 'eu-central-003', s3_bucket = 'devxy-rpkgs-binaries', s3_access_key_id = Sys.getenv('B2_S3_ACCESS_KEY'), s3_secret_access_key = Sys.getenv('B2_S3_SECRET_KEY'))"
-        for RBIN in /opt/R/*/bin/R; do
+        for RBIN in /opt/R/[0-9]*/bin/R; do
           RMINOR=$(basename "$(dirname "$(dirname "$RBIN")")" | cut -d. -f1-2)
           /opt/R/$R_VERSION/bin/R -q -e "bincraft::upload_package_index(codename = '$CODENAME', r_minor = '$RMINOR', s3_endpoint = 'https://s3.eu-central-003.backblazeb2.com', s3_region = 'eu-central-003', s3_bucket = 'devxy-rpkgs-binaries', s3_access_key_id = Sys.getenv('B2_S3_ACCESS_KEY'), s3_secret_access_key = Sys.getenv('B2_S3_SECRET_KEY'))" || true
         done