feat(verisimdb): add 47 VQL end-to-end integration tests

Comprehensive E2E tests covering the full VQL pipeline:
- Full pipeline round-trips (parse → typecheck → execute) for all 8 modalities
- Proof certificate round-trips for all 11 proof types (typecheck → generate → verify)
- Multi-proof AND composition with batch cert generation/verification
- Tampered certificate detection (SHA-256 integrity)
- Cross-modal condition evaluation (drift, consistency, exists, compound AND)
- Mutation pipeline (INSERT/UPDATE/DELETE via parse_statement)
- Pagination invariants (LIMIT/OFFSET preservation)
- Federation queries with all 4 drift policies (STRICT/REPAIR/TOLERATE/LATEST)
- Error paths (empty query, gibberish, unknown proofs, modality mismatches)

All tests pass with and without Rust core running.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: hyperpolymath