ci: remove GitHub CI — native git.hanzo.ai + cd.hanzo.ai only

This workflow ran on a self-hosted actions-runner-controller pool. ARC is
decommissioned: CI executes inside git.hanzo.ai (Gitea Actions, .hanzo/workflows)
and delivery is cd.hanzo.ai reconciling the reviewed image pin in
hanzoai/universe. GitHub is a mirror and runs nothing.

Removed rather than repointed — there is no GitHub-side pool to move to, and
leaving it would keep ARC load-bearing.

.github/workflows/deploy.yml

@@ -1,26 +0,0 @@
-name: Deploy to GitHub Pages
-
-on:
-  push:
-    branches: [main, master]
-  workflow_dispatch:
-
-permissions:
-  contents: write
-  pages: write
-  id-token: write
-
-jobs:
-  deploy:
-    runs-on: hanzo-deploy-linux-amd64
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Deploy to GitHub Pages
-        uses: peaceiris/actions-gh-pages@v4
-        with:
-          github_token: ${{ secrets.GITHUB_TOKEN }}
-          publish_dir: ./
-          publish_branch: gh-pages
-          exclude_assets: '.github,README.md,LICENSE,.gitignore'