chore: remove github workflows

using tangled CI now

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[e-mail]>

.github/workflows/ci.yml

···
-name: CI
-
-on:
-  push:
-    branches: [main]
-  pull_request:
-  schedule:
-    - cron: "0 0 * * 0"  # weekly
-
-jobs:
-  lint:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - uses: mlugg/setup-zig@v2
-      - run: zig fmt --check .
-
-  test:
-    strategy:
-      matrix:
-        os: [ubuntu-latest, macos-latest]
-    runs-on: ${{ matrix.os }}
-    steps:
-      - uses: actions/checkout@v4
-      - uses: mlugg/setup-zig@v2
-      - run: zig build test --summary all