fix(creating): resolve duplicate content in index.ts files during create mode

[imjuni]

Summary

• Fix duplicate content issue in index.ts files when running ctix in create mode
• Remove duplicate directory processing that caused same export statements to be written twice

Test plan

• Analyze the root cause of duplicate content generation
• Implement deduplication logic in createModeFiles processing
• Verify that each directory is processed only once

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (10d87c2) to head (21da535).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #185   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           88        88           
  Lines         2183      2185    +2     
  Branches       424       424           
=========================================
+ Hits          2183      2185    +2     

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