fix(core): remediate validation feedback loss and access control regressions

[envsecure]

Description

This PR provides a comprehensive fix for the critical regressions in the KeystoneJS core that were identified in CI logs following the submission of PR #9838. It essentially replaces and completes the work started in #9838 by addressing the specific failure cases found in automated testing.

Key Improvements:

1. Validation Pipeline Restoration:

   • Reverted internal error tags from validate to validateInput. This is a crucial fix for the API test suite which explicitly matches on the validateInput tag.
   • Restored the complex generic type signatures in hooks.ts to resolve MISSING_EXPORT build errors encountered with Rollup/Preconstruct.
   • Fixed a logic regression where field-level validation messages were being swallowed if a list-level hook crashed.

2. Access Control Robustness:

   • Updated checkUniqueItemExists to correctly handle lists that are hidden from the GraphQL schema due to access control.
   • It now transforms "schema not supported" errors into the standard "Access denied ... it may not exist" message, ensuring consistent security-by-obscurity behavior.
   • Infrastructure-related database errors are now correctly rethrown instead of being masked.

3. CI & Formatting:

   • Standardized formatting in hooks.ts to strictly adhere to the KeystoneJS "no semicolon" and trailing newline rules, resolving the format:check failures.

Changes

• packages/core/src/lib/core/hooks.ts: Fixed types, formatting, and error tags.
• packages/core/src/lib/core/access-control.ts: Improved error handling for unique item checks.
• .changeset/remediate-ci-failures.md: Added documentation for the patch.

Relation to Previous Work

• Supersedes: fix(core): remediate validation feedback loss and access control silent errors #9838
• Fixes: CI regressions introduced in fix(core): preserve field validation messages on list hook crash #9837 and fix(core): remediate validation feedback loss and access control silent errors #9838.