Seed pre-commit cache from main builds

[bdice]

Run the shared checks workflow as a style-only job on main builds so it writes the pre-commit cache, and make PR checks restore that cache read-only.

Today pre-commit cache entries are scoped to each PR's merge ref, which other PRs cannot read. The first style check on every PR runs cold, and the per-PR entries fill the repository's GitHub Actions cache quota.

Mirrors NVIDIA/cudf#24093.

Part of rapidsai/build-planning#332.

[coderabbitai]

Navigate logical layers of code changes, visualize relationships, and explore their blast radius.

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository: NVIDIA/raft/.coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 723d3a88-c92b-4d33-bda1-35702437d9d4

📥 Commits

Reviewing files that changed from the base of the PR and between 2677357 and d8d2cc5.

📒 Files selected for processing (2)

• .github/workflows/build.yaml
• .github/workflows/pr.yaml

Included review availability: This review used your included allowance. Your plan provides up to 12 included reviews per hour; 10 remain after this review.

---

📝 Summary

Summary by CodeRabbit

• Chores
  • Updated automated validation for the main branch and pull requests to keep project checks consistent and reduce duplicate build cache archives. These changes affect development workflows only; no end-user features or application behavior have changed.

Walkthrough

The build workflow adds a checks job that runs on the main branch and calls the shared checks workflow with specified checks disabled. The pull request workflow sets pre-commit cache use to read-only.

Changes

Checks workflow configuration

Layer / File(s)	Summary
Configure checks workflows .github/workflows/build.yaml, .github/workflows/pr.yaml	The build workflow adds a main-only checks job with read permissions and specified checks disabled. The pull request workflow sets pre-commit-cache-read-only to true and adds comments about cache use.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to d8d2c

The workflow configuration supports seeding the pre-commit cache from main and restoring it read-only on pull requests. No concrete merge-blocking issue is established.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: seeding the pre-commit cache from main builds.
Description check	✅ Passed	The description directly explains the workflow changes, cache behavior, motivation, and related references.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Commit to this branch
• Create a new PR

🧪 Generate unit tests (beta)

• Create a new PR

• Autopilot · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

Autopilot is currently an internal CodeRabbit preview.

---

_{Comment @coderabbitai help to get the list of available commands.}