docs: range-read M4 (openUrl in the browser): changelog, limits, design status

CHANGELOG (Unreleased), known-issues (the browser can open URLs; the
limits of openUrl: round trips per wave of misses, a call holds what it
reads, CORS and validator visibility, the download fallback), the M4
status in docs/design/range-reads.md (why NeedBytes rather than a
Worker, why not clawhdf5-remote's BlockCache, what was tested; the
status paragraph at the top lost a garbled duplicate), the viewer's
README (API, options, how it works, tests; the size table is marked as
predating openUrl), CLAUDE.md and the README crate list.

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

README.md

@@ -757,7 +757,7 @@ clawhdf5 workspace (19 crates, ~86K lines of Rust in src/, ~104K with tests
 ├── Bindings
 │   ├── clawhdf5-py          — Python (PyO3)
 │   ├── clawhdf5-napi        — Node.js (napi-rs)
-│   └── clawhdf5-wasm        — Browser (WebAssembly, wasm-bindgen; read-only)
+│   └── clawhdf5-wasm        — Browser (WebAssembly, wasm-bindgen; read-only; remote files by HTTP range requests)
 │
 └── Tooling
     ├── clawhdf5-tools       — h5rs: ls, dump, stat, diff, check