fix(ci): job timeouts everywhere + retries on all network installs

Reliability pass over every workflow:
- timeout-minutes on all 21 jobs that lacked one (a hung job previously
  burned the 6-hour default runner budget)
- ./.github/actions/retry wrapped around every network-fetching install
  that lacked it: pip installs (deploy-site, skills-index), npm ci
  (deploy-site website, upload_to_pypi web + ui-tui), uv sync (docker
  test deps). Deterministic build steps (npm run build) deliberately
  NOT retried — split into separate steps so a real build failure fails
  fast instead of retrying 3x.

.github/workflows/tests.yml

@@ -20,6 +20,7 @@ jobs:
   generate:
     name: "Generate slices"
     runs-on: ubuntu-latest
+    timeout-minutes: 10
     outputs:
       matrix: ${{ steps.matrix.outputs.matrix }}
     steps:
@@ -126,6 +127,7 @@ jobs:
     needs: test
     if: needs.test.result == 'success' && github.ref == 'refs/heads/main'
     runs-on: ubuntu-latest
+    timeout-minutes: 10
     steps:
       - name: Download all slice durations
         uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1