B6: add a WASM binding test suite

The WASM binding had no tests; CI only checked that artefacts existed.
Adds a wasm-bindgen-test suite covering SMA reference values, EMA
batch==streaming equivalence, RSI pure-uptrend behaviour, fallible
constructors returning JsError, and the unequal-length batch guards from
B3. Wires wasm-pack test --node into the CI wasm job. The suite
type-checks on the host; it executes under wasm-pack in CI (the local
environment is a non-rustup Rust install without the wasm32 target).

.github/workflows/ci.yml

@@ -112,6 +112,9 @@ jobs:
       - name: Build WASM package
         run: wasm-pack build bindings/wasm --target web --release --features panic-hook
 
+      - name: Run WASM tests
+        run: wasm-pack test --node bindings/wasm
+
       - name: Verify generated artefacts
         run: |
           test -f bindings/wasm/pkg/wickra_wasm.js