docs: indexed name lookups and checked address conversion (M0)

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

docs/design/range-reads.md

@@ -379,6 +379,15 @@ fast path within benchmark noise.
   n children decodes its links O(n) times. Look names up through the index
   (above) and let a listing hand out its entries, so the cache has less to
   absorb.
+- *Status 2026-09-26:* done on branch `perf/p3-indexed-lookups` — link and
+  attribute names through the name indexes (`group_v2::resolve_child`,
+  `attribute::find_attribute_in_file`; creation-order lookups by name do
+  not exist in the API, so the creation-order index is still only listed),
+  `addr::to_usize`/`saturating_usize` for all 115 `u64 as usize` casts in
+  `clawhdf5-format` (the 133 above counted any `*addr*/*offset* as usize`,
+  mostly widening `u8`/`u32` casts; `scripts/check-32bit-casts.sh` lints
+  wasm32 for the truncating ones), and `Group::entries`/`File::group_at`.
+  The facade, io and ann casts are not converted.
 
 **M1 — metadata over the trait, in-memory impl identical to today (2–3 weeks).**
 - Add `Storage` (above) to `clawhdf5-format`, `no_std`-compatible, with