[JohnVillalovos]

The whole tree is clean at level 4, so raise phpstan.neon to level 4. There is no baseline and no ignored error.

Move phpstan_next.neon to level 5 and exclude the areas that still report errors there (891 errors in 202 files), so each can be fixed and removed from the list in its own PR, as was done for levels 3 and 4.

Update the documented level in AGENTS.md.

Closes: #735
Assisted-by: Claude:claude-opus-5-5

[Copilot]

🔵 Needs a closer look

The PHPStan level changes and exclusions cannot be validated here because confirming the 891 diagnostics and level-4 clean result requires running the repository’s CI analysis with installed dependencies.

No open issues 🎉

What changed in this PR

Raises the repository’s enforced PHPStan level from 3 to 4 and begins a staged level 5 rollout with exclusions for areas that still report errors. Documentation is updated to reflect the new baseline.

Changes:

• Enforces PHPStan level 4 in phpstan.neon.
• Sets phpstan_next.neon to level 5 with staged exclusions.
• Updates AGENTS.md to document PHPStan level 4.

File	Description
phpstan.neon	Raises the primary PHPStan analysis level to 4.
phpstan_next.neon	Raises progressive analysis to level 5 and excludes areas with outstanding diagnostics.
AGENTS.md	Updates static-analysis documentation to reflect PHPStan level 4.

_{Review effort: Lite}