ci(screenshots): bump Actions to Node 24 majors

[evinaeva]

Why

GitHub removes Node 20 from Actions runners on 2026-09-16 (force-migration of Node 20 actions to Node 24 began 2026-06-16). The Screenshots workflow still pinned actions/checkout@v4 + actions/setup-node@v4 (both Node 20 actions) — the same exposure PR #107 fixed for deploy.yml, and which that PR explicitly flagged as a follow-up. This is that follow-up. Per the Node 20 deprecation changelog.

What changed — .github/workflows/screenshots.yml

Each action bumped to its latest major (both Node 24-based; latest tags verified via the GitHub API — checkout v6.0.3, setup-node v6.4.0):

Action	Before	After
actions/checkout	v4	v6
actions/setup-node	v4	v6

This workflow does not use the Pages actions, so the upload-pages-artifact dotfile breaking change handled in PR #107 does not apply here.

Breaking changes reviewed — none affect this workflow

• checkout v6 — "persist creds to a separate file" (#2286). This is the one to watch, because unlike deploy.yml this workflow runs a bare git push origin HEAD:... in a later step that relies on the credentials checkout persists. v6 no longer writes the token's http.<origin>/.extraheader inline into .git/config; it writes it to a creds file in RUNNER_TEMP and adds an includeIf.gitdir:<gitDir>.path pointer in the local .git/config. A subsequent git push from the workspace resolves the same gitdir, includes the creds file, and authenticates exactly as before — the change is transparent to consumers. v6.0.0/v6.0.1 additionally added includeIf entries for worktrees, which is relevant since scripts/screenshots.mjs makes per-version worktrees (though those are local/read-only and don't need creds).
• setup-node v5 auto-cache (#1348), narrowed to npm in v6 (#1374). Auto-caching only triggers when package.json has a packageManager field — this repo has none, so behavior is identical to v4 (no caching, no "lock file not found" error). A package-lock.json exists as a fallback regardless.
• Both v6 actions require runner v2.327.1+; GitHub-hosted ubuntu-latest is well past that (and already runs v6 via deploy.yml).

node-version: 20 left as-is

The setup-node node-version: 20 input is the project runtime for the screenshots scripts — a separate concern from the action runtime, and out of scope for this deprecation fix. setup-node downloads the requested Node version from the actions/node-versions manifest, so it keeps working after Node 20 leaves the runners' preinstalled toolcache on 2026-09-16. (Happy to bump the runtime deliberately in a separate change if desired.)

Verification

• ✅ checkout v6.0.3 and setup-node v6.4.0 confirmed as the latest majors via gh api repos/<a>/releases/latest.
• ✅ YAML parses; only the two uses: lines changed (@v4 → @v6), structure untouched.
• This workflow is workflow_dispatch-only (manual), so it won't run on push and isn't exercised by PR CI — it's run on demand from Actions → "Screenshots" → Run workflow.

🤖 Generated with Claude Code