test: exceed 75% Vitest coverage across all metrics and resolve RLS schema bug

[jdjdjjdrjnsn]

Resolves #71
/claim #71

Summary of Changes

Achieves >75% test coverage across all four Istanbul metrics on the entire repository and resolves the schema-matching issue in the Row Level Security (RLS) plugin:

1. Test Coverage Metrics (All thresholds met)

• Statements: 96.71% (Required: 75%)
• Branches: 82.43% (Required: 75%)
• Functions: 97.84% (Required: 75%)
• Lines: 96.97% (Required: 75%)
• Test Results: 25/25 test files passing, 284/284 tests passing.

2. Suites Added & Expanded

• ****: Complete suite covering admin bypass, disabled mode, source table filtering, and rejection logging.
• ****: Covers SQLite header stripping, multiline comments, and formData parsing error paths.
• ****: Covers plugin registry registration, retrieval, and UnimplementedError recovery.
• ** & **: Comprehensive CSV import route coverage and quoted CSV field splitting.
• ****: Comprehensive coverage for Durable Object transactions, alarm rescheduling, and error propagation.
• ****: Covers transaction validation, plugin pre-auth routing, and error handlers.
• ****: Covers data source fallbacks, Hyperdrive query errors, and external connections.
• ****: Covers top-level Worker export, CORS preflight, and request dispatching.
• ** & **: Fixes schema-aware table matching so that schema-qualified policy definitions properly match unqualified table queries and subqueries.

All tests run cleanly with zero regressions on .