[2.2.9] Improve build time - #3022

Thanks — the four items outside the threads, in order.

npm install -> npm ci. Deliberate, and I would keep install. ci installs the lockfile exactly, which freezes @arduino/docs-arduino-cc at the pinned version: today a theme release reaches the sites because install re-resolves it, and with ci every release would need a lockfile bump in each consumer repo first. npm ci is the better verb for a lockfile-driven deploy in general — it just conflicts with how this project ships the theme. The speed argument is also weaker than it looks here: with the warm npm cache and --prefer-offline --no-audit --fund=false the step went from 2.5 min to 0.6-0.8 min, which is the win we were after.

Action majors one or two behind. Deliberate for this PR. We learned the cost the hard way: bumping Node 18 -> 22 added node22 to the cache keys, which correctly invalidated every existing entry and cost one run 29 minutes of gatsby-plugin-sharp. Stacking three more major jumps into the same PR while we are measuring build time mixes the variables. Happy to do them as a follow-up, where a regression is attributable.

xargs … || echo swallowing a systemic failure. You are right, fixed. The install is now followed by command -v jpegoptim > /dev/null && command -v optipng > /dev/null, so a missing compressor stops the job while the per-file tolerance stays for the handful of .png files that are really JPEGs (three of them, all in content/hardware/09.kits/maker/iot-bundle, if anyone wants to fix them at the source).

Third checkout attempt without timeout-minutes. Reworded so it reads as a choice: "one more wipe and a last try, bounded by the job timeout".