ci: collapse superseded runs with a per-ref concurrency group

[ErikBjare]

Mirrors ActivityWatch/aw-server-rust#804: adds a per-workflow, per-ref concurrency group to build.yml, codeql.yml, examples.yml, lint.yml.

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: ${{ github.event_name == 'pull_request' }}

On PRs, a new push cancels the superseded run. On master, a running build always finishes, and only queued runs collapse to the newest commit, so a merge burst doesn't queue a full build per commit while master still gets regular per-commit results.

Release workflows are deliberately untouched (there are none in this repo).

[ErikBjare]

@greptileai review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-10T16:12:17.797942Z	28a08ff	PR opened

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[greptile-apps]

Confidence Score: 5/5

[High impact] The PR appears safe to merge.

Summary

Adds separate concurrency groups for each workflow and ref across all four CI workflows.

• Build, CodeQL, Examples, and Lint replace superseded runs per ref.

No actionable issues were found.

_{Reviews (1) · Last reviewed commit: "ci: collapse superseded runs with a per-..." · Reviewed by Greptile}