fix(mft): restore OFFLINE path sorting (5/6 SORTED MATCH)

[githubrobbi]

Summary

Restores OFFLINE MFT processing to 5/6 SORTED MATCH state after regression from commit 90ee522.

What was broken

• Commit 90ee522 removed ALL sort_directory_children() calls for C++ parity (Drive S fix)
• This broke OFFLINE path — all 6 drives went from 5/6 SORTED MATCH to 0/6 output

Fix

1. Re-added sort_directory_children() to OFFLINE paths:

   • persistence.rs (loading saved index)
   • merge.rs (post-processing)
   • builder.rs (already fixed by previous agent)

2. Fixed verify_parity.rs to use --format custom for C++ footer parity

Result

• ✅ Drive D: SORTED MATCH (7,065,330 lines)
• ✅ Drive E: SORTED MATCH (2,929,497 lines)
• ❌ Drive F: MISMATCH (Bug 3 - extension records, deferred)
• ✅ Drive G: SORTED MATCH (15,071 lines)
• ✅ Drive M: SORTED MATCH (1,908,783 lines)
• ✅ Drive S: SORTED MATCH (8,278,080 lines)

5/6 SORTED MATCH restored ✅

🤖 Generated with Claude Code