[Stephen Griffin (stephenegriffin)]

Summary

Hide the remaining IConverterSession menu commands behind the existing Enable legacy features option (off by default):

• Advanced > Import / Export > Convert MSG to EML
• Advanced > Import / Export > Convert EML to MSG
• Folder > Import > From EML

Existing windows update on the next menu opening, before context-sensitive enabled states are calculated. Restored commands retain resource-backed labels, original ordering, and owner-draw behavior. The already-gated export dropdown and MrMAPI remain unchanged. Code-only change; no documentation changes.

Closes #291 through the agreed legacy-UI gating approach. This does not claim to fix NDR conversion or install IConverterSession.

Validation

• Debug Unicode x64 and x86 builds passed.
• Production-linked UI checks passed on both architectures: initial off/on states and 28 live-menu state checks, including no duplicates, preserved ordering and owner-draw labels, unchanged non-converter menu structure, and EML import disabled without a folder.
• Real export dialogs: four formats without EML when off; five including EML when on.
• clang-format 17 and git diff --check passed.
• UI checks are session-only integration diagnostics, not additional permanent UnitTest coverage. No mailbox access, converter activation, or settings persistence was required.

[github-actions]

Test Results

    8 files  ±0      8 suites  ±0   51s ⏱️ +8s
  288 tests ±0    288 ✅ ±0  0 💤 ±0  0 ❌ ±0 
2 304 runs  ±0  2 304 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 29dffee. ± Comparison against base commit 463cc00.