ci(bazel): harden detect matching + cap matrix concurrency

[balajinvda]

Why

Two follow-ups to the change-aware detect job restored in #424:

1. CodeRabbit flagged that printf ... | grep -q under set -o pipefail can misfire: grep -q closes the pipe on its first match, printf can take SIGPIPE (141), and pipefail then makes the whole pipeline non-zero. In an if, a real match reads as no-match, so a subtree gets silently dropped from the matrix. This is the exact "tests skipped without anyone noticing" failure mode we are trying to prevent.
2. A full matrix starts ~20 jobs at once, and every runner pulls actions/checkout from codeload.github.com simultaneously, tripping GitHub's action-download rate limit (HTTP 429 in "Set up job"). This has been failing docs-era PRs (docs: update 0.6.1 release candidate manifest #423) and re-runs.

What changed

1. Replace all four printf '%s\n' "$changed" | grep -q ... sites with a here-string (grep -q PATTERN <<<"$changed"). No pipe, no SIGPIPE, no pipefail interaction. The awk pipelines are unaffected (awk drains stdin, never early-exits).
2. Add max-parallel: 8 to the bazel matrix so the checkout burst stays under the rate limit. Change-aware scheduling keeps most PRs below the cap; full-matrix events (a workflow change, main push, workflow_dispatch) run in batches.

Customer Release Notes

Not customer visible (CI-only).

Testing

YAML validated; confirmed no printf | grep -q remain and here-strings preserve the existing anchored patterns.

References

Follow-up to #424. CodeRabbit review comment on that PR.

Summary by CodeRabbit

• Chores
  • Improved workflow change detection to ensure more consistent scheduling of relevant builds.
  • Limited parallel execution of Bazel-related CI jobs to reduce startup/burst load and improve stability.
  • Updated the displayed name for Bazel required checks to be clearer.

[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: Enterprise

Run ID: dbbbd4f3-4e55-44b3-b462-69d89c3cdb5e

📥 Commits

Reviewing files that changed from the base of the PR and between ca16617 and 830e395.

📒 Files selected for processing (1)

• .github/workflows/bazel.yml

🚧 Files skipped from review as they are similar to previous changes (1)

• .github/workflows/bazel.yml

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📝 Walkthrough

Walkthrough

The Bazel workflow updates changed-file matching in the detect job, caps Bazel and Docker matrix concurrency, and renames the verification job display label.

Changes

Bazel workflow scheduling

Layer / File(s)	Summary
Changed-file detection matching .github/workflows/bazel.yml	The detect job replaces printf/grep pipelines with here-string checks for workflow, Java framework, root .bzl, and path-prefix changes.
Bazel matrix concurrency .github/workflows/bazel.yml	The bazel and bazel-docker matrix strategies set max-parallel to 8 and 4.
Required-check job labeling .github/workflows/bazel.yml	The bazel-verification display name changes to “bazel required checks”.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• NVIDIA/nvcf#424: Both update Bazel workflow change-aware scheduling logic.

Suggested reviewers: kristinapathak

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title follows Conventional Commits and accurately describes this CI-only Bazel workflow change.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ci/harden-bazel-matrix

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