Fix structure formatting to hide link IDs in output

[konard]

Summary

Fixed a bug where the --structure option was displaying link IDs in the formatted output instead of showing a clean nested structure representation.

Before: (4:(2:(1: ) 1) 2)
After: ((( ) 1) 2)

Changes Made

• Modified Program.cs to change the FormatStructure call parameters from (true, true) to (false, false)
• This disables showing link IDs in the structure representation, providing cleaner output

Test Plan

• Reproduced the original issue locally
• Verified the fix produces the expected output format
• Tested structure formatting for multiple link IDs (1, 2, 3, 4)
• Confirmed all structure outputs now match the expected clean format

Verification

# Create test links
dotnet run --project Foundation.Data.Doublets.Cli -- '() ((1: 0 0))'
dotnet run --project Foundation.Data.Doublets.Cli -- '() ((2: 1 1))' 
dotnet run --project Foundation.Data.Doublets.Cli -- '() ((3: 2 1))'
dotnet run --project Foundation.Data.Doublets.Cli -- '() ((4: 2 2))'

# Test structure formatting
dotnet run --project Foundation.Data.Doublets.Cli -- --structure 4
# Output: ((( ) 1) 2)   ✅ Clean nested structure

Fixes #19

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