ci: lint all targets, run interop suites for real, compile benches

- clippy --all-targets plus a clawhdf5-format feature matrix (parallel, lz4,
  zstd, pcodec, fast-checksum); fix the accumulated lint backlog in test,
  bench and feature-gated code (no behaviour changes).
- Install python3 + h5py/numpy/netCDF4/xarray in the CI container and set
  CLAWHDF5_REQUIRE_INTEROP=1, which makes a missing interop dependency a test
  failure. Every h5py/netCDF4 interop test used to skip silently in CI. Run
  the #[ignore]d writer_h5py_tests suite explicitly.
- cargo bench --no-run so benches can't rot; fix bench.rs and memory_bench.rs,
  which no longer compiled against the current strategy/consolidation APIs.
- Optional fuzz smoke run via CLAWHDF5_FUZZ_SECONDS.
- CHANGELOG and docs/known-issues.md updated.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

crates/clawhdf5/tests/h5py_interop_tests.rs

@@ -10,6 +10,12 @@ use clawhdf5::{AttrValue, CompoundTypeBuilder, DType, File, FileBuilder};
 // Helpers
 // ---------------------------------------------------------------------------
 
+/// When `CLAWHDF5_REQUIRE_INTEROP=1` (set in CI), a missing Python dependency
+/// is a test failure instead of a silent skip.
+fn interop_required() -> bool {
+    std::env::var("CLAWHDF5_REQUIRE_INTEROP").is_ok_and(|v| v == "1")
+}
+
 fn python_available() -> bool {
     Command::new("python3")
         .args(["-c", "import h5py; print(h5py.__version__)"])
@@ -21,6 +27,10 @@ fn python_available() -> bool {
 macro_rules! skip_if_no_python {
     () => {
         if !python_available() {
+            assert!(
+                !interop_required(),
+                "CLAWHDF5_REQUIRE_INTEROP=1 but python3 with h5py is not available"
+            );
             eprintln!("SKIP: python3 with h5py not available");
             return;
         }