test: Fix disabled test_tableverbpack_writes_be64_when_modern

[jsavin]

Problem

Test was disabled in PR #125 at db_format_tests.c:283-285 because it creates only a minimal table structure, but the refactored pack functions now enforce preconditions that require a complete structure.

Root Cause

After the mode stack refactor:

• Pack functions require flinmemory=1 precondition (external must be in memory)
• Pack functions expect fully initialized table structures
• Test was creating minimal tyhashtable with only fldirty/flsubsdirty fields

What's Needed

1. Create properly initialized tyhashtable structure with:

   • All required fields initialized
   • Valid nodedata structure
   • Proper subtable entries (if needed)

2. Remove the early return at db_format_tests.c:285

3. Verify test passes with complete structure

References

• PR Refactor: Complete mode stack elimination for deterministic migration #125: Refactor: Complete mode stack elimination for deterministic migration
• db_format_tests.c:282-337 (test function)
• Common/headers/hash.h (tyhashtable structure definition)

Priority

P3 - Low priority (production migration works, internal test only)
Related: PR #125 (closed as minor known issue)

[jsavin]

Fixed in commit f5f4231: test re-enabled with proper test isolation and complete table structure initialization. Test is now running and passing in db_format_tests.c:285-371.