docs: add expanded verifiable bug review artifacts

[bryancasler]

Motivation

• Expand previous senior-level review artifacts to cover additional verifiable runtime issues discovered in packages/scripts/src that were missing from the earlier writeup.
• Provide reproducible evidence and suggested fixes for issues that can cause runtime crashes, configuration corruption, or incorrect UI/validation behavior.
• Keep the review as documentation-only so maintainers can triage and fix the faults without introducing behavioral changes.

Description

• Add CODE_REVIEW.md containing three engrid-focused findings for ENGrid.deepMerge, ENGrid.getOption, and ENGrid.getUrlParameter with reproduction snippets and expected vs actual outcomes.
• Add docs/senior-code-review-verifiable-bugs.md containing three additional verifiable findings for remember-me.ts, min-max-amount.ts, and country-disable.ts including verification steps and suggested fixes.
• Preserve the previously added SENIOR_CODE_REVIEW.md content without changes.
• All changes are documentation-only and do not modify runtime source code.

Testing

• Verified the new files exist and contain the expected content by printing their contents and confirming structure for CODE_REVIEW.md (75 lines), SENIOR_CODE_REVIEW.md (17 lines), and docs/senior-code-review-verifiable-bugs.md (66 lines).
• Performed repository sanity checks to ensure the documentation files were written and readable and that the added review sections are present.
• Confirmed that the update is documentation-only with no source files altered.
• All validation steps completed successfully.

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Codex Task