ci: expose cpu_parallel_mode and run planner tests with -n 0

[dmitry-tokarev-nv]

Summary

• Add cpu_parallel_mode input (default 'auto') to shared-test.yml, build-test-distribute-flavor.yml, and the matrix wrapper; forward it to the pytest action's existing parallel_mode.
• Override to '0' for planner callers in pr.yaml (planner-test) and post-merge-ci.yml (planner-pipeline) to address OOM / flakiness observed with xdist auto.
• All other callers retain the auto default — no behavior change outside planner.

Test plan

• PR CI: planner-test step logs 📊 Parallelization: disabled (sequential execution) for GPU runs and passes.
• CPU-only test steps for vllm/sglang/trtllm continue to log 📊 Parallelization: auto.
• Post-merge planner-pipeline runs -n 0 after merge.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Chores
  • Made CPU test parallelization configurable in CI workflows, allowing selection of execution modes (auto, none, or custom worker counts) across build and test pipelines instead of using hardcoded defaults.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: fe4060a9-1dbe-4dc7-ba35-a7fd3edf61f7

📥 Commits

Reviewing files that changed from the base of the PR and between 4ef2894 and 4acb5fc.

📒 Files selected for processing (5)

• .github/workflows/build-test-distribute-flavor-matrix.yml
• .github/workflows/build-test-distribute-flavor.yml
• .github/workflows/post-merge-ci.yml
• .github/workflows/pr.yaml
• .github/workflows/shared-test.yml

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Walkthrough

GitHub Actions workflows are updated to add a configurable cpu_parallel_mode input parameter that controls pytest-xdist parallelization behavior for CPU-only tests. This replaces hardcoded 'auto' values with a configurable input (default 'auto'), allowing workflow callers to override the parallelization mode. GPU tests remain sequential with parallel_mode: 'none'.

Changes

Cohort / File(s)	Summary
Workflow Input Definitions .github/workflows/build-test-distribute-flavor-matrix.yml, .github/workflows/build-test-distribute-flavor.yml, .github/workflows/shared-test.yml	Added new workflow input cpu_parallel_mode (type: string, default: 'auto') for controlling pytest-xdist parallelization. CPU-only test steps updated to use this input instead of hardcoded values.
Workflow Consumer Updates .github/workflows/post-merge-ci.yml, .github/workflows/pr.yaml	Added cpu_parallel_mode: '0' to workflow calls invoking reusable test workflows, configuring sequential CPU-only test execution.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description covers the changes and test plan, but is missing required sections from the template: Overview section is absent, Details section is incomplete, no specific file callouts for review, and Related Issues section is missing.	Add Overview section summarizing the change, complete Details section, add 'Where should the reviewer start?' with specific files, and include Related Issues section with issue reference.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main changes: exposing a cpu_parallel_mode input and running planner tests with sequential execution (-n 0).
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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