ci: update docs build uv version (#2648)

Successful run: https://github.com/CQCL/hugr/actions/runs/18872234455

Author: ss2165

.github/workflows/docs.yml

@@ -15,6 +15,11 @@ permissions:
   pages: write
   id-token: write
 
+env:
+  UV_VERSION: "0.9.5"
+  UV_FROZEN: 1
+  UV_PYTHON: "3.14"
+
 # Allow only one concurrent deployment, skipping runs queued between the run
 # in-progress and latest queued.
 concurrency:
@@ -37,10 +42,8 @@ jobs:
       - name: Set up uv
         uses: astral-sh/setup-uv@v6
         with:
-          version: "0.4.18"
+          version: ${{ env.UV_VERSION }}
           enable-cache: true
-      - name: Install Python
-        run: uv python install 3.14
 
       - name: Build docs
         run: |