ci: require CPU regression tests before merging

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ci-${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  cpu-tests:
+    name: CPU tests (Python ${{ matrix.python }})
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    strategy:
+      fail-fast: false
+      matrix:
+        python: ['3.10', '3.12']
+    steps:
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
+      - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
+        with:
+          python-version: ${{ matrix.python }}
+          cache: pip
+          cache-dependency-path: requirements-ci.txt
+      - name: Install CPU test environment
+        run: |
+          python -m pip install -r requirements-ci.txt
+          python -m pip install torch==2.7.0 --index-url https://download.pytorch.org/whl/cpu
+          python -m pip install --no-deps -e .
+      - name: Run CPU regression suite
+        run: bash scripts/test_cpu_ci.sh
+      - name: Upload test report
+        if: always()
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
+        with:
+          name: cpu-tests-python-${{ matrix.python }}
+          path: reports/cpu-tests.xml
+          if-no-files-found: warn
+          retention-days: 14
+
+  ci-required:
+    name: CI required
+    if: always()
+    needs: [cpu-tests]
+    runs-on: ubuntu-latest
+    timeout-minutes: 2
+    steps:
+      - name: Require all CPU test jobs to pass
+        env:
+          RESULT: ${{ needs.cpu-tests.result }}
+        run: test "$RESULT" = success

docs/ci.md

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+# Continuous integration and merge policy
+
+Pushes to any branch and pull requests targeting `main` run `.github/workflows/ci.yml`.
+The workflow can also be started manually from GitHub Actions.
+
+The CPU regression suite runs on Python 3.10 and 3.12 with PyTorch 2.7.0 CPU.
+It covers configuration, asynchronous execution, phase tracing, reload control,
+legacy and cost-aware CMLFQ, rollout clients, and CPU-offload backend orchestration.
+The explicit test list lives in `scripts/test_cpu_ci.sh`; add new CPU-safe tests there.
+This is a selected regression suite, not the entire repository test suite.
+
+To reproduce in a clean Python 3.10–3.12 virtual environment:
+
+```bash
+python -m pip install -r requirements-ci.txt
+python -m pip install torch==2.7.0 --index-url https://download.pytorch.org/whl/cpu
+python -m pip install --no-deps -e .
+bash scripts/test_cpu_ci.sh
+```
+
+JUnit reports are uploaded for 14 days. Jobs have timeouts and superseded runs
+are cancelled. `CI required` succeeds only when every matrix job passes;
+failed, cancelled, or skipped dependencies do not satisfy the gate.
+No path filters are used, so documentation-only PRs also receive the required check.
+PR workflows use read-only permissions, hosted runners, and no cluster credentials.
+
+The `main` branch protection requires a PR and the GitHub Actions `CI required`
+check on an up-to-date branch, including administrators. Force pushes and deletion
+are disabled. No reviewer approval is required by this initial policy; a maintainer
+still merges manually after checks pass. GitHub branch protection is repository
+configuration, separate from this workflow file; changing YAML alone does not
+activate it. This setup does not publish packages or deploy training services.
+
+CUDA kernel, vLLM connector, multi-GPU KV migration, and full RL throughput
+validation remain manual cluster tests using `scripts/validate_cpu_offload.slurm`
+and `scripts/benchmark_scheduler_rl.slurm`. CPU CI does not certify GPU correctness
+or performance. Public PR code is not automatically executed on HPC-GMC.

requirements-ci.txt

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+# CPU-only CI dependencies; intentionally excludes the CUDA runtime stack.
+pytest==8.3.5
+pytest-asyncio==0.26.0
+numpy==1.26.4
+PyYAML==6.0.2
+httpx==0.28.1

scripts/test_cpu_ci.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+cd "$(dirname "$0")/.."
+python -m pytest -q --strict-markers --junitxml=reports/cpu-tests.xml \
+  tests/test_config_parsing.py \
+  tests/test_qwen3_config.py \
+  tests/test_async_task_runner.py \
+  tests/test_phase_tracer.py \
+  tests/test_restartable_vllm_server.py \
+  tests/test_cmlfq_scheduler.py \
+  tests/test_cmlfq_cost_scheduler.py \
+  tests/test_hetero_cmlfq_integration.py \
+  tests/test_rollout_engine.py \
+  tests/test_cpu_offload_backend.py