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/label-base-on-title.yml

@@ -1,30 +0,0 @@
-name: "Auto-label PRs based on title"
-
-on:
-  pull_request_target:
-    types: [opened, reopened]
-
-jobs:
-  add-label-if-prefix-matches:
-    permissions:
-      contents: read
-      pull-requests: write
-    runs-on: hanzo-build-linux-amd64
-    steps:
-      - name: Check PR title and add label if it matches prefixes
-        uses: actions/github-script@v7
-        continue-on-error: true
-        with:
-          script: |
-            const title = context.payload.pull_request.title.toLowerCase();
-            const prefixes = ['chore', 'ci', 'style', 'test', 'refactor'];
-            
-            // Check if the PR title starts with any of the prefixes
-            if (prefixes.some(prefix => title.startsWith(prefix))) {
-              await github.rest.issues.addLabels({
-                owner: context.repo.owner,
-                repo: context.repo.repo,
-                issue_number: context.payload.pull_request.number,
-                labels: ['skip-release-notes']
-              });
-            }