ci: replace IS_GITEA var with server_url detection

Updates the docs deployment and notebook test workflows to automatically
detect the running environment using `github.server_url`. This removes
the dependency on the manual `IS_GITEA` variable, ensuring that Gitea
deployment jobs run correctly on self-hosted instances and are skipped
on GitHub.com.

Author: SamoraHunter

.github/workflows/docs.yml

@@ -86,7 +86,7 @@ jobs:
   # Deploy job for GitHub Pages
   deploy-github:
     needs: build
-    if: ${{ vars.IS_GITEA != 'true' }}
+    if: ${{ github.server_url == 'https://github.com' }}
     environment:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}
@@ -114,7 +114,7 @@ jobs:
   # Deploy job for Gitea
   deploy-gitea:
     needs: build
-    if: ${{ vars.IS_GITEA == 'true' }}
+    if: ${{ github.server_url != 'https://github.com' }}
     runs-on: ubuntu-latest
     env:
       NODE_EXTRA_CA_CERTS: /etc/ssl/certs/ca-certificates.crt

.github/workflows/notebook-test.yml

@@ -28,7 +28,7 @@ jobs:
             echo "TORCH_CPU_ONLY=true" >> $GITHUB_ENV
           fi
 
-          if [[ "${{ vars.IS_GITEA }}" == "true" ]]; then
+          if [[ "${{ github.server_url }}" != "https://github.com" ]] && [[ -z "${{ env.ACT }}" ]]; then
             echo "Setting thread limits for Gitea runner"
             echo "OMP_NUM_THREADS=1" >> $GITHUB_ENV
             echo "MKL_NUM_THREADS=1" >> $GITHUB_ENV