[alexandrewavelet]

Why

Follow-up of #158 / #159. While prod ran PHP 8.4.27 and preprod still 7.4, the PHP lint/test job ran on a ['7.4', '8.4'] matrix so that no change could break preprod's runtime. Since Altered-Re-Union/AlteredOps#21, both environments run PHP 8.4.27 (checked on X-Powered-By for altered.re and website-preprod.altered.re), so the 7.4 leg no longer protects anything.

What changes

• plugins-ci.yml: the "PHP lint and plugin PHP tests" job goes back to a single 8.4 run, under its original name. The jobs that needs: it use its id (php), which is unchanged, and the aggregated Plugins CI check still covers it.
• CONTRIBUTING.md, README.md, design-system/AGENTS.md: stop asking for PHP 7.4-compatible code. PHP 8 syntax is fine; keep new code free of 8.5-only features.

No PHP code changes.

Notes

• main gets these doc changes with the next preprod → main sync. Until then its CONTRIBUTING still mentions the 7.4 lint on preprod.
• PHP 8 syntax is now allowed, 8.4 features included. No rule is kept on 8.3 compatibility for now; a rollback goes to another 8.4.x release.

🤖 Generated with Claude Code

[github-actions]

⚠️ Loading: CLS over budget

Not a failure: the CLS of a screen varies from one CI run to the next. Each screenshot is the settled page, the boxes that moved drawn on it (dashed: before, solid: after). Frame by frame: npm run loading:timeline -- <screen> in tests/e2e. Run: https://github.com/Altered-Community/alteredcore-website/actions/runs/39697479688

desktop · editor, Main, second visit at 1024 px: skeleton until the first screen, styled, no layout shift

CLS 0.2211 (budget 0.01)

Shifts

1210 ms  0.0004
  x600 y111 87×24 → x522 y111 165×24 (ac-badge.ac-badge.ac-badge--orange < button.legality < app-deck-bar.reduced)
1323 ms  0.2207
  x24 y306 652×494 → x24 y791 652×9 (h2.overline < app-hand-stats < div.hand)
  x356 y533 320×256 → x0 y0 0×0
  x24 y533 320×256 → x0 y0 0×0
  x357 y474 318×46 → x0 y0 0×0
  x373 y421 286×36 → x0 y0 0×0

desktop · editor, Main, second visit at 1280 px: skeleton until the first screen, styled, no layout shift

CLS 0.2018 (budget 0.01)

Shifts

1116 ms  0.0006
  x623 y111 217×24 → x545 y111 217×24 (img < ac-badge.ac-badge < ac-rarity-limits)
  x856 y111 87×24 → x778 y111 165×24 (ac-badge.ac-badge.ac-badge--orange < button.legality < app-deck-bar.reduced)
  x606 y97 1×52 → x528 y97 1×52 (span.sep < app-deck-bar.reduced < div.top)
1226 ms  0.2012
  x24 y306 908×466 → x0 y0 0×0
  x157 y242 147×40 → x181 y242 171×40 (button.ac-button.ac-button--secondary < div.toolbar < app-test-hand)
  x24 y796 908×4 → x0 y0 0×0