ci: wire up CI, fix no_std build, fix stale package names in scripts

- Add .gitea/workflows/ci.yml running scripts/ci-test.sh (fmt, clippy,
  test, no_std check) on push/PR to main.
- Fix stale rustyhdf5-py/rustyhdf5-format package names in
  ci-test.sh/check-nostd.sh, which had been silently no-op'ing those
  checks (cargo warns but doesn't fail on an unknown --exclude/-p
  target).
- With those checks actually running, fix the real issues they surface:
  - clippy: useless_conversion in chunked_write.rs, byte_char_slices in
    global_heap.rs/object_header.rs.
  - cargo fmt: apply formatting across the workspace (whitespace only).
  - no_std (thumbv7em-none-eabihf) build errors in clawhdf5-format:
    core::sync::atomic::AtomicU64 doesn't exist on that target (no
    native 64-bit atomics) — switch profiling.rs's counters to
    portable-atomic, which falls back to a CAS-based emulation there
    and is a no-op wrapper elsewhere. Add missing alloc imports for
    Box (filters.rs), Vec (filters_szip.rs), and format! (dict_encoding.rs)
    on no_std paths. Replace f64::powi (std/libm-only) with a small
    local exponentiation-by-squaring helper in the scale-offset filter.

crates/clawhdf5-bench/benches/h5bench_meta.rs

@@ -41,11 +41,7 @@ fn bench_metadata_attrs_write(c: &mut Criterion) {
             let path = tmp.path().join("attrs_libhdf5.h5");
             b.iter(|| {
                 let file = hdf5::File::create(&path).unwrap();
-                let ds = file
-                    .new_dataset::<f64>()
-                    .shape([3])
-                    .create("data")
-                    .unwrap();
+                let ds = file.new_dataset::<f64>().shape([3]).create("data").unwrap();
                 ds.write(&[1.0f64, 2.0, 3.0]).unwrap();
                 for i in 0..k {
                     ds.new_attr::<i64>()
@@ -258,11 +254,7 @@ fn bench_metadata_open_from_disk(c: &mut Criterion) {
         let libhdf5_path = tmp.path().join("open_libhdf5.h5");
         {
             let file = hdf5::File::create(&libhdf5_path).unwrap();
-            let ds = file
-                .new_dataset::<f64>()
-                .shape([3])
-                .create("data")
-                .unwrap();
+            let ds = file.new_dataset::<f64>().shape([3]).create("data").unwrap();
             ds.write(&[1.0f64, 2.0, 3.0]).unwrap();
             ds.new_attr::<i64>()
                 .create("label")
@@ -307,13 +299,17 @@ fn bench_metadata_parse_in_memory(c: &mut Criterion) {
         fb.finish().unwrap()
     };
 
-    group.bench_with_input(BenchmarkId::new("clawhdf5", "in_memory"), &bytes, |b, raw| {
-        b.iter(|| {
-            let file = File::from_bytes(raw.clone()).unwrap();
-            let ds = file.dataset("data").unwrap();
-            ds.attrs().unwrap()
-        });
-    });
+    group.bench_with_input(
+        BenchmarkId::new("clawhdf5", "in_memory"),
+        &bytes,
+        |b, raw| {
+            b.iter(|| {
+                let file = File::from_bytes(raw.clone()).unwrap();
+                let ds = file.dataset("data").unwrap();
+                ds.attrs().unwrap()
+            });
+        },
+    );
 
     group.finish();
 }