Sync merge/release workflows with PR CI updates

[ggrell]

Motivation

• Ensure non-PR CI workflows are consistent with recent Pull Request workflow updates to avoid CI drift and tooling mismatches.
• Provide the required Codecov token environment in all coverage upload steps so coverage reporting behaves the same across workflows.

Description

• Bumped ruby/setup-ruby from Ruby 2.6 to 3.2 in .github/workflows/merge_master.yml and .github/workflows/publish_release.yml.
• Added CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }} to the Codecov upload steps in both merge_master.yml and publish_release.yml so the bash <(curl -s https://codecov.io/bash) upload uses the token.
• Committed the changes to the current branch and prepared a PR titled "Sync merge/release workflows with PR CI updates".

Testing

• ruby -e "require 'yaml'; ['.github/workflows/merge_master.yml','.github/workflows/publish_release.yml','.github/workflows/pull_request.yml'].each{|f| YAML.load_file(f)}; puts 'yaml-ok'" succeeded indicating the workflow YAML files parse.
• git diff --check succeeded with no whitespace or conflict markers reported.
• python - <<'PY' ... import yaml ... PY attempt failed due to missing PyYAML in the environment, which is an environment limitation rather than a workflow syntax issue.

---

Codex Task

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.11%. Comparing base (cfc13bc) to head (c1ea3a4).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #307   +/-   ##
=========================================
  Coverage     88.11%   88.11%           
  Complexity       48       48           
=========================================
  Files             9        9           
  Lines           101      101           
=========================================
  Hits             89       89           
  Misses           12       12           

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0471d5d...c1ea3a4. Read the comment docs.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.