ci: add GitHub Actions workflow on self-hosted Apple Silicon runners

Adds lint (ruff) and pytest jobs running on the OSPO-provisioned
[self-hosted, macos, tahoe, ARM64] runners; the DSL/composite tests
require Metal + MLX on Apple Silicon. Jobs are guarded to apple/coreai-torch
so forks can't claim the self-hosted pool.

Author: DawerG

.github/workflows/ci.yml

@@ -0,0 +1,31 @@
+name: CI
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  lint:
+    if: github.repository == 'apple/coreai-torch'
+    runs-on: [self-hosted, macos, tahoe, ARM64]
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/setup-uv@v4
+      - run: uv run --extra dev ruff check .
+      - run: uv run --extra dev ruff format --check .
+
+  python-test:
+    if: github.repository == 'apple/coreai-torch'
+    runs-on: [self-hosted, macos, tahoe, ARM64]
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/setup-uv@v4
+      - run: uv run --extra test pytest tests/ -n auto -m "not slow"