Resolve #3627678 "Fix the phpcs"

Makes the phpcs, phpstan and cspell jobs pass and makes them blocking. One commit per job.

• cspell: project dictionary for our own terms, cspell:ignore for the French test strings, extension/dist/ excluded.
• phpcs: comments wrapped to 80 characters, missing docs written, long arrays split.
• phpstan: $cacheability added to the entity operation hooks; tests no longer use the deprecated PageRegion class directly.

phpstan-baseline.neon ignores the last 2 errors, which #3620535 fixes. Delete it once that's in.

Note for #3620535: its latest commit adds 3 new violations, which will fail once these jobs are blocking.

Closes #3627678