Clean up CI: remove boilerplate workflows, add Julia CI

Removed template workflows not relevant to Julia packages (ts-blocker,
npm-bun-blocker, guix-nix-policy, jekyll, etc.). Added standard Julia
CI workflow where missing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/ci.yml

@@ -0,0 +1,38 @@
+# SPDX-License-Identifier: MPL-2.0
+name: CI
+permissions: read-all
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    name: Julia ${{ matrix.julia-version }} - ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        julia-version: ['1.10', '1.11']
+        os: [ubuntu-latest]
+        include:
+          - julia-version: '1.11'
+            os: macos-latest
+
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+
+      - uses: julia-actions/setup-julia@4c0cb0fce8556fdb04a90347310e5db8b1f98fb9 # v2
+        with:
+          version: ${{ matrix.julia-version }}
+
+      - uses: julia-actions/cache@e33b4bfa0ea7cd9caedd7cb82b0e36956ef40285 # v2
+
+      - name: Install, build, test
+        run: julia --project=. -e 'using Pkg; Pkg.instantiate(); Pkg.build(); Pkg.test()'