format: checked chunk addresses on the parallel read path

Three `chunk_info.address as usize` casts behind the `parallel` feature
survived the conversion, because check-32bit-casts.sh linted only default
features plus plugin-filters. On a 32-bit target with rayon a chunk address
past 4 GiB still wrapped onto another part of the file. They go through
addr::to_usize now, and the lane index (h % n, always < n) through
saturating_usize.

The script now lints no default features, default features, and every
optional feature but szip (wasm32; the set with zstd, which does not build
for wasm32, on the host, where the lint reports the same casts). With the
old parallel_read.rs/lane_partition.rs it fails listing the four casts; the
old script passed them. CHANGELOG and the design note give the exact count
(119) and what is not covered.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

scripts/check-32bit-casts.sh

@@ -5,8 +5,18 @@
 # of the file. File values go through `addr::to_usize` (a clean error) and
 # in-memory counts through `addr::saturating_usize`.
 #
-# Lints wasm32-unknown-unknown with clippy's cast_possible_truncation and
-# fails on any u64 -> usize finding (other truncations are not checked here).
+# Lints with clippy's cast_possible_truncation and fails on any u64 -> usize
+# finding (other truncations are not checked here), once per feature set
+# below. Together the sets compile every feature-gated line of the crate that
+# ci-test.sh builds: features only add code, except `not(feature = ...)`
+# paths for std/checksum/fast-checksum/szip, which the no-default-features
+# and default sets cover. szip is left out (it needs libaec), as in
+# ci-test.sh.
+#
+# The sets are linted for wasm32 where they build there. zstd links a C
+# library that does not build for wasm32, so the set with it is linted for
+# the host: the lint reports u64 -> usize casts whatever the target's
+# pointer width, and the crate has no pointer-width-dependent code.
 #
 # Usage:
 #   ./scripts/check-32bit-casts.sh
@@ -16,19 +26,42 @@
 
 set -euo pipefail
 
-TARGET="wasm32-unknown-unknown"
-echo "==> Checking for truncating u64 -> usize casts in clawhdf5-format ($TARGET)"
+WASM="wasm32-unknown-unknown"
+ALL_BUT_ZSTD="parallel,lz4,pcodec,fast-checksum,blake3_hash,plugin-filters,lookup-stats"
 
-out=$(cargo clippy -p clawhdf5-format --target "$TARGET" \
-    --features plugin-filters --message-format short \
-    -- -A clippy::all -W clippy::cast_possible_truncation 2>&1) || {
-    echo "$out"
-    echo "==> clippy failed" >&2
-    exit 1
-}
-found=$(grep -F 'casting `u64` to `usize`' <<<"$out" || true)
-if [ -n "$found" ]; then
-    echo "$found"
+# target|cargo feature arguments
+SETS=(
+    "$WASM|--no-default-features"
+    "$WASM|--no-default-features --features std,checksum"
+    "$WASM|"
+    "$WASM|--features $ALL_BUT_ZSTD"
+    "host|--features $ALL_BUT_ZSTD,zstd"
+)
+
+status=0
+for set in "${SETS[@]}"; do
+    target=${set%%|*}
+    args=${set#*|}
+    target_args=()
+    if [ "$target" != host ]; then
+        target_args=(--target "$target")
+    fi
+    echo "==> Checking for truncating u64 -> usize casts in clawhdf5-format ($target: ${args:-default features})"
+    # shellcheck disable=SC2086 # $args is a list of arguments
+    out=$(cargo clippy -p clawhdf5-format "${target_args[@]}" $args \
+        --message-format short \
+        -- -A clippy::all -W clippy::cast_possible_truncation 2>&1) || {
+        echo "$out"
+        echo "==> clippy failed" >&2
+        exit 1
+    }
+    found=$(grep -F 'casting `u64` to `usize`' <<<"$out" || true)
+    if [ -n "$found" ]; then
+        echo "$found"
+        status=1
+    fi
+done
+if [ "$status" -ne 0 ]; then
     echo "==> use addr::to_usize (file values) or addr::saturating_usize (in-memory counts)" >&2
     exit 1
 fi