Switch back to stable rust version for wasm tests

The ubuntu-latest image uses Node v18, which isn't compatible with
wasm-bindgen-test when building with Rust 1.82+ due to the use of LLVM's
`reference-types` feature, see:
rustwasm/wasm-bindgen#4211

ubuntu-24.04 includes Node v20 which doesn't have the same problem,
allowing the wasm tests to move back to stable.

.github/workflows/ci.yml

@@ -96,11 +96,11 @@ jobs:
         run: just check_links
 
   wasm:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
 
     steps:
       - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@1.81.0
+      - uses: dtolnay/rust-toolchain@stable
         with:
           targets: wasm32-unknown-unknown
       - uses: jetli/wasm-pack-action@v0.4.0

crates/koto/examples/wasm/README.md

@@ -11,3 +11,7 @@ To build and open the example site, `cd` to this folder and run:
 npm install
 npm run start
 ```
+
+## Dependencies
+
+Since Rust `1.82`, Node `v20` is required to run the tests.