Fix re-entrancy and redundant saves in profile rename handlers

[Copilot]

Addresses code review feedback on PR #1 (profile rename feature): eliminates PropertyChanged re-entrancy loops, removes redundant I/O, and improves migration robustness.

Changes

Re-entrancy prevention in OnProfileNameChanged

• Added _isUpdatingProfileName guard flag to prevent infinite loops when programmatically reverting or adjusting profile names
• Added early exit when name hasn't changed vs. store

Optimized RenameProfile I/O

• Skip file write and timestamp update when resolved name equals current name
• Trim input before uniqueness resolution

Robust migration detection in ProfileStore.Load

• Replaced string-based JSON search with object-level duplicate/missing ID detection before normalization
• Handles minified JSON and formatting variations correctly

Cleanup consistency in SyncManager

• Clear _profileNames alongside _syncGroups when sync is disabled

Test hygiene

• Log warnings on test directory cleanup failure instead of silent catch

// Before: setting pi.Name triggers PropertyChanged recursively
pi.Name = finalName;  // Re-enters OnProfileNameChanged

// After: guarded assignment prevents re-entrancy
_isUpdatingProfileName = true;
try { pi.Name = finalName; }
finally { _isUpdatingProfileName = false; }

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