fix: Add missing activation events and test coverage for audit P0 items

Addresses third audit findings by adding missing command activation events
and creating test coverage for ignoredFromRemoval specifier sorting.

Key changes:
- Added onCommand activation events for checkConflicts and toggleLegacyMode
- Previously only imports.organize had explicit activation event
- All 3 commands now activate extension when invoked (VS Code best practice)

Test improvements:
- Created test 99: ignoredFromRemoval libraries have sorted specifiers
- Verifies that protected libraries maintain consistent formatting
- Confirms implementation at import-manager.ts:555-562 works correctly
- Test PASSES - implementation was already correct, now has coverage

Audit analysis results:
- P0 items: All resolved (syntax errors, activation events, regex schema)
- P1 items: Determined to be non-issues (historical test counts, config passthrough)
- P2 items: All addressed

Test status: 335/335 main tests passing, 191/191 comparison tests passing

This completes the third audit response cycle with all critical items
resolved and proper test coverage in place.

Author: JohannesHoppe