GOOWOO-740: Update CI workflows for Node.js 24 compatibility

[mserino]

Changes proposed in this Pull Request:

Closes GOOWOO-740.

Description:
GitHub runners began defaulting to Node 24 on June 16, 2026, deprecating Node 20 actions. This PR updates all workflows in this repo to be Node 24-compatible.

Changes:

• codecov/codecov-action: bumped SHA pin from v4.6.0 to v5.5.4. v4 is a JS action declaring runs: using: node20; v5 switched to a composite/shell implementation, eliminating the node runtime dependency entirely.
• woocommerce/grow actions: bumped all usages from @actions-v2 to @actions-v3 across 11 workflow files. The actions-v3 tag was released June 12, 2026 specifically for node24 compatibility — notably get-plugin-releases now declares runs: using: node24, and prepare-node now calls actions/setup-node@v6 (previously @v4).

Known limitations not addressed in this PR:

• update-browserslist-db.yml still uses c2corg/browserslist-update-action@v2.5.0, which declares runs: using: node20. v2.5.0 is the latest release and the main branch has no node24 update.
• run-qit.yml still uses woocommerce/grow/run-qit-extension@actions-v2 — this action was intentionally removed from actions-v3 as broken and unused (grow#239). The file has been removed
• deploy.yml has node_version: '20' — this controls the Node.js version used to build the plugin, not the runner runtime. It's tied to .nvmrc and is a separate concern.

Screenshots:

Detailed test instructions:

1. No node20 deprecation warnings in any workflow run after merging. Previously these appeared as yellow annotations on every run; they should be gone for all updated workflows.
2. js-unit-tests — verify the codecov upload step completes without errors.
3. php-unit-tests — same for the codecov upload step.
4. branch-labels, js-css-linting, php-coding-standards, php-hook-documentation, post-release-merge — these run on PR/push events; open a test PR to trigger them and confirm they pass.
5. update-browserslist-db.yml will still show a node20 warning — that's expected and documented.

Additional details:

Changelog entry

Dev - Update GitHub Actions workflows to Node.js 24: bump woocommerce/grow from @actions-v2 to @actions-v3, actions/checkout from @v4 to @v6, codecov/codecov-action from v4 to v5, and remove unused run-qit.yml workflow.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.8%. Comparing base (99adf60) to head (ed961fc).
⚠️ Report is 14 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##             develop   #3519     +/-   ##
===========================================
- Coverage       67.7%   66.8%   -0.9%     
  Complexity      5322    5322             
===========================================
  Files            518     913    +395     
  Lines          21453   28226   +6773     
  Branches           0    1720   +1720     
===========================================
+ Hits           14513   18855   +4342     
- Misses          6940    9110   +2170     
- Partials           0     261    +261     

Flag	Coverage Δ
js-unit-tests	64.1% <ø> (?)
php-unit-tests	67.7% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.
see 395 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[mikaeltomovic]

Hey @mserino, great work on this! It's mostly very good and I think you have covered all workflows consistently. However I found a few things you might want to double check.

1. The PR description says deploy.yml has node_version: '20' but that doesn't match what's in ‎.github/workflows/deploy.yml on line 47. I think your reasoning in the description is correct and that this should be left at 20 since .nvmrc still runs 20.
2. If you look at ‎.github/workflows/js-unit-tests.yml (line 43) and .github/workflows/php-unit-tests.yml (line 115) you'll see uses: codecov/codecov-action@b9fd7d16f6d7d1b5d2bec1a2887e65ceed900238 # v4.6.0 which I believe pins codecov to version 4.6.0 (to this commit more specifically). I think you'll have to update this line to another PIN. The PR description says you "bumped SHA pin from v4.6.0 to v5.5.4. v4 is a JS action declaring runs: using: node20; v5 switched to a composite/shell implementation, eliminating the node runtime dependency entirely." but this bump doesn't seem to be included.