Install Mojo SDK in codspeed benchmark CI for vortex-array

Adds a pip install step for the Mojo SDK in the bench-codspeed job,
gated to only run for the vortex-array shard. This enables the Mojo
AOT take/filter kernels during codspeed benchmark runs so we get
performance tracking for the SIMD gather path.

Signed-off-by: Claude <noreply@anthropic.com>

https://claude.ai/code/session_01EVcJZP4ZmfvWRRg2CsgvST

Author: claude

.github/workflows/ci.yml

@@ -743,6 +743,11 @@ jobs:
         uses: taiki-e/cache-cargo-install-action@66c9585ef5ca780ee69399975a5e911f47905995
         with:
           tool: cargo-codspeed
+      - name: Install Mojo SDK
+        if: contains(matrix.packages, 'vortex-array')
+        run: |
+          pip install --user mojo
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
       - name: Build benchmarks
         env:
           RUSTFLAGS: "-C target-feature=+avx2"