Clean PHPUnit bootstrap and PHP 8.4 deprecations

What

Make the PHPUnit bootstrap clean on PHP 8.4 by removing duplicate custom-table installation notices and addressing actionable dependency deprecations observed during #1805.

Why

Tests pass, but noisy bootstrap output can hide real database failures and future PHP compatibility regressions. Interrupted runs can also leave the disposable test schema incomplete.

Tier

tier:standard — the investigation spans the WordPress test bootstrap, Ultimate Multisite installers, BerlinDB table creation, and pinned validation dependencies.

Files

• tests/bootstrap.php
• inc/class-requirements.php or the verified requirements implementation
• inc/installers/ database setup paths
• composer.json and composer.lock if dependency updates are required
• Focused installer/bootstrap tests

Reference pattern

Reproduce with an empty disposable wptests_ schema and XDEBUG_MODE=off vendor/bin/phpunit --filter WP_Ultimo_Main_Test. Verify installed dependency versions and local exports before changing third-party compatibility code.

Implementation steps

1. Trace why custom wptests_wu_* tables are created more than once during bootstrap.
2. Make installation idempotent without suppressing genuine database errors.
3. Separate WordPress-core deprecations from plugin/dependency deprecations.
4. Update or patch pinned dependencies only when verified against local package source.
5. Add a regression test for clean repeated bootstrap or installer execution.

Acceptance criteria

• Focused tests produce no duplicate-table database notices.
• Plugin-owned PHP 8.4 deprecations are removed.
• External WordPress-core-only notices are documented separately if unavoidable.
• Repeated installer execution remains idempotent.
• Focused and full PHPUnit runs pass.

Verification

• XDEBUG_MODE=off vendor/bin/phpunit --filter WP_Ultimo_Main_Test
• XDEBUG_MODE=off vendor/bin/phpunit
• pnpm run quality

Dependency

Blocked by #1805; begin after PR #1806 merges.

aidevops.sh v3.32.317 plugin for OpenCode v1.18.29 with gpt-5.6-sol spent 4h 26m and 539,830 tokens on this with the user in an interactive session.

Reproduce the issue with an empty disposable wptests_ schema using the focused PHPUnit command, then trace tests/bootstrap.php and the inc/installers/ database setup paths for repeated custom-table creation. Check inc/class-requirements.php, composer.json, and composer.lock before assessing dependency deprecations. Done means focused and full PHPUnit runs are clean, repeated installation is idempotent, and unavoidable WordPress-core notices are documented separately.