pages.yml: actually install Emscripten before building WASM

web/step0_emsdk_install.sh is a one-liner that just clones the emsdk
wrapper repo. The toolchain itself — emsdk/upstream/emscripten/, which
the cmake -DCMAKE_TOOLCHAIN_FILE arg points at — lands via the
install+activate pair that step1_emsdk_activate_linux.sh does locally.
pages.yml was calling step0 but never the install/activate steps, so the
WASM build always failed at cmake-configure ("Could not find toolchain
file"). continue-on-error: true on this step paints it green in the run
summary, and the post-build staging silently skipped the missing-artifact
copies — until the round-5 placeholder gate started serving the
"Runtime rebuild in progress" page instead, which is what surfaced this.

Add the two missing commands. The build should now actually produce
web/output/daslang_static.{js,wasm}; the existing staging gate will then
take the real path instead of the placeholder.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: borisbat

.github/workflows/pages.yml

@@ -77,8 +77,14 @@ jobs:
       run: |
         set -eux
         cd web
+        # step0 only clones the emsdk wrapper — the toolchain itself
+        # (emsdk/upstream/emscripten/) lands via the install+activate pair
+        # that web/step1_emsdk_activate_linux.sh does locally. Without these,
+        # cmake's -DCMAKE_TOOLCHAIN_FILE points at a path that doesn't
+        # exist yet and the WASM build silently fails under continue-on-error.
         bash step0_emsdk_install.sh
-        # step1 sources emsdk_env.sh — re-export EMSDK for the configure step
+        ./emsdk/emsdk install latest
+        ./emsdk/emsdk activate latest
         bash -c "source emsdk/emsdk_env.sh && \
                  mkdir -p build && cd build && \
                  cmake -DCMAKE_BUILD_TYPE=Release -G Ninja \