Update terminology around xorbs and CAS objects.

[hoytak]

This PR updates the internal documentation of the xet package to reflect a recent pass to make "xorb" consistently refer to the data objects we use to store chunks, and "cas" consistently refer to the remote server / data store. Previously, both "xorb" and "cas" referred to the data object, which caused some confusion.

---

Note

Medium Risk
Mostly terminology/comment updates, but the regenerated chunker_wasm_bg.js changes wasm-bindgen glue code (externref table indices, added stream adapters), which could affect runtime chunking behavior if mismatched with the wasm module or consumers.

Overview
Updates internal Xet terminology to consistently describe stored chunk containers as xorbs (vs previously calling them CAS blocks), including ReconstructionInfo docs and shard footer field comments in shardParser.ts/uploadShards.ts.

Regenerates the vendored wasm-bindgen JS wrapper (chunker_wasm_bg.js), updating externref table plumbing, adding stream-related adapter classes (IntoUnderlying*), and slightly reshaping the exported Chunker wrapper (method ordering and new closure/helpers).

^{Written by Cursor Bugbot for commit 3222eae. This will update automatically on new commits. Configure here.}

[coyotte508]

Comments ok but regarding the WASM update, do you know why the changes? It's also bigger now

Is there any signifcant benefit from the new WASM? (bug fixes/behavior changes impacting chunks / merkle tree / blake3 hash?)

Would be worth running a bench mark - there's huggingface/huggingface.js/packages/xetchunk-wasm/tests/bench.js . Originally it's meant to compare Xet's thin WASM against JS/WASM mix, but it can be run with both old & new thin wasm to compare perf - if it's a perf upgrade

---

in any case the doc changes on their own are fine, I just don't want to include a bigger wasm in the JS lib without good reason