format: monomorphise the Storage parsers so local files stay as fast

Every `*_in` core and the read helpers take `file: &S` with
`S: Storage + ?Sized` instead of `&dyn Storage`, and the `&[u8]`
wrappers pass the slice itself, so they compile to a `[u8]` instance:
`as_contiguous()` inlines to `Some(self)` and each structure read is the
slice code's bounds check again, with no indirect call. `&dyn Storage`
still works (`S = dyn Storage`); there is one parser implementation.

Also, so the structure reads cost no more than the slice checks did:
- ObjectHeader::parse_in reads the prefix once (signature included)
  instead of the signature and then the prefix: two reads for a
  one-chunk header instead of three on a range backend;
- the symbol-table node and group B-tree (v1) loops walk their entries
  with chunks_exact over the bytes read, and the node's redundant second
  bounds check is gone (the entries' read is the check, same error);
- a version-1 header's message list is sized from its (capped) count.
Same results and errors; the unit and equivalence tests are unchanged.

New Criterion bench `clawhdf5/benches/local_metadata_bench.rs` over a
400-group version-1 file written by h5py (new fixture
`v1_groups_400.h5`): ObjectHeader::parse, symbol-table nodes, the group
B-tree walk and a facade listing, using only APIs that exist at f2ff2c4
so it builds there for an A/B.

Provisional A/B against f2ff2c4 (busy machine, not for docs): both
builds linked into one binary and timed in alternation, 200 rounds;
median ratio new/old: facade listing -0.5% to -3.5% (was +14%),
ObjectHeader::parse +1% to +2% (was +25%), symbol-table nodes -18%,
group B-tree walk -18%, local-heap names and resolve_group_children
within +-1.5%. An old-vs-old-copy run shows +-2% from code layout alone.

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

crates/clawhdf5-format/src/fractal_heap.rs

@@ -139,13 +139,13 @@ impl FractalHeapHeader {
         offset_size: u8,
         length_size: u8,
     ) -> Result<FractalHeapHeader, FormatError> {
-        Self::parse_in(&file_data, offset as u64, offset_size, length_size)
+        Self::parse_in(file_data, offset as u64, offset_size, length_size)
     }
 
     /// [`Self::parse`] over any [`Storage`]: one read of the header (two
     /// when it holds an I/O filter pipeline).
-    pub fn parse_in(
-        file: &dyn Storage,
+    pub fn parse_in<S: Storage + ?Sized>(
+        file: &S,
         offset: u64,
         offset_size: u8,
         length_size: u8,
@@ -382,15 +382,15 @@ impl FractalHeapHeader {
         id_bytes: &[u8],
         offset_size: u8,
     ) -> Result<Vec<u8>, FormatError> {
-        self.read_managed_object_in(&file_data, id_bytes, offset_size)
+        self.read_managed_object_in(file_data, id_bytes, offset_size)
     }
 
     /// [`Self::read_managed_object`] over any [`Storage`]. A huge object
     /// found through the huge-object v2 B-tree still needs the whole file
     /// in memory ([`FormatError::ContiguousStorageRequired`] otherwise).
-    pub fn read_managed_object_in(
+    pub fn read_managed_object_in<S: Storage + ?Sized>(
         &self,
-        file_data: &dyn Storage,
+        file_data: &S,
         id_bytes: &[u8],
         offset_size: u8,
     ) -> Result<Vec<u8>, FormatError> {
@@ -423,7 +423,11 @@ impl FractalHeapHeader {
     }
 
     /// Read a huge object (heap ID type 1).
-    fn read_huge_object(&self, file: &dyn Storage, id: &[u8]) -> Result<Vec<u8>, FormatError> {
+    fn read_huge_object<S: Storage + ?Sized>(
+        &self,
+        file: &S,
+        id: &[u8],
+    ) -> Result<Vec<u8>, FormatError> {
         let os = usize::from(self.offset_size);
         let ls = usize::from(self.length_size);
         // (address, stored length, filter mask, decoded length); the last two
@@ -475,9 +479,9 @@ impl FractalHeapHeader {
 
     /// Look up huge object `key` in the huge-object v2 B-tree, returning
     /// (address, stored length, filter mask, decoded length).
-    fn find_huge_record(
+    fn find_huge_record<S: Storage + ?Sized>(
         &self,
-        file: &dyn Storage,
+        file: &S,
         key: u64,
     ) -> Result<(u64, u64, u32, u64), FormatError> {
         if is_undefined(self.huge_btree_address, self.offset_size) {
@@ -554,9 +558,9 @@ impl FractalHeapHeader {
     }
 
     /// Read a managed object (heap ID type 0).
-    fn read_heap_managed(
+    fn read_heap_managed<S: Storage + ?Sized>(
         &self,
-        file_data: &dyn Storage,
+        file_data: &S,
         id_bytes: &[u8],
         offset_size: u8,
     ) -> Result<Vec<u8>, FormatError> {
@@ -604,9 +608,9 @@ impl FractalHeapHeader {
     /// header), so we just add it to the block address minus the block's heap
     /// offset. A filtered heap stores each direct block (header included)
     /// through its filter pipeline, so the block is decoded first.
-    fn read_from_direct_block(
+    fn read_from_direct_block<S: Storage + ?Sized>(
         &self,
-        file: &dyn Storage,
+        file: &S,
         block: DirectBlock,
         target_offset: u64,
         length: usize,
@@ -645,9 +649,9 @@ impl FractalHeapHeader {
 
     /// Read an object by traversing an indirect block to find the right direct block.
     #[allow(clippy::too_many_arguments)]
-    fn read_from_indirect_block(
+    fn read_from_indirect_block<S: Storage + ?Sized>(
         &self,
-        file: &dyn Storage,
+        file: &S,
         iblock_addr: usize,
         nrows: u16,
         iblock_heap_offset: u64,