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-format/tests/reference_tests.rs

@@ -180,15 +180,20 @@ print('ok')
     let output = match output {
         Ok(o) if o.status.success() => o,
         _ => {
+            // CI sets CLAWHDF5_REQUIRE_INTEROP=1 so this can't silently skip.
+            assert!(
+                !std::env::var("CLAWHDF5_REQUIRE_INTEROP").is_ok_and(|v| v == "1"),
+                "CLAWHDF5_REQUIRE_INTEROP=1 but python3 with h5py is not available"
+            );
             eprintln!("skipping h5py_object_reference_roundtrip: python3+h5py not available");
             return;
         }
     };
     let stdout = String::from_utf8(output.stdout).unwrap();
-    if !stdout.trim().contains("ok") {
-        eprintln!("skipping h5py_object_reference_roundtrip: h5py script failed");
-        return;
-    }
+    assert!(
+        stdout.trim().contains("ok"),
+        "h5py reference-file generator did not report ok: {stdout}"
+    );
 
     // Read the file and parse object references
     let file_data = std::fs::read(&path).unwrap();