fix(ci): wasm-pack PATH + Dockerfile workspace stub

Closes the two post-merge failures from #436:

1. wasm-pack: command not found — cargo install doesn't reliably leave
   the binary on PATH. Switched to the canonical installer in both the
   Pages and a11y workflows.
2. nvsim-server Docker build — cargo couldn't resolve workspace.dependencies
   from a partial copy. Dockerfile now generates a stub workspace
   Cargo.toml inline that lists just nvsim + nvsim-server.

Co-Authored-By: claude-flow <ruv@ruv.net>

.github/workflows/dashboard-a11y.yml

@@ -24,7 +24,8 @@ jobs:
       - uses: dtolnay/rust-toolchain@stable
         with: { targets: wasm32-unknown-unknown }
 
-      - run: cargo install wasm-pack --locked --version 0.13.x || true
+      - name: Install wasm-pack
+        run: curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh
 
       - name: Build nvsim WASM
         working-directory: v2

.github/workflows/dashboard-pages.yml

@@ -43,7 +43,9 @@ jobs:
           restore-keys: ${{ runner.os }}-cargo-nvsim-
 
       - name: Install wasm-pack
-        run: cargo install wasm-pack --locked --version 0.13.x || true
+        run: |
+          curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh
+          which wasm-pack
 
       - name: Build nvsim WASM
         working-directory: v2