refactor: Refactor sync modifiers to use shared Data1D processing logic

[andeplane]

Problem

After extracting the common Data1D processing logic (see issue #185), the three sync modifiers need to be refactored to use the shared function, keeping only their unique logic.

Current Behavior

Each sync modifier (synccomputesmodifier.ts, syncfixesmodifier.ts, syncvariablesmodifier.ts) contains ~125 lines, with most of it being duplicated Data1D processing logic.

Expected Behavior

Refactor all three modifiers to:

• Call the shared processData1D() helper function
• Keep only the unique logic:
  • Which sync method to call (syncComputes(), syncFixes(), syncVariables())
  • Which name array to get (getComputeNames(), getFixNames(), getVariableNames())
  • Which collection to update in output (output.computes, output.fixes, output.variables)
• Reduce each file from ~125 lines to ~50-60 lines

Files to Modify

• src/modifiers/synccomputesmodifier.ts
• src/modifiers/syncfixesmodifier.ts
• src/modifiers/syncvariablesmodifier.ts

Prerequisites

• Issue refactor: Extract common Data1D processing logic from sync modifiers #185 must be completed first (extraction of shared Data1D processing logic)

Benefits

• Significant reduction in code duplication
• Easier to maintain and test
• Consistent behavior across all sync modifiers
• Makes it easier to add new modifiers in the future

Implementation Notes

Each modifier should:

1. Call the appropriate sync method (syncComputes, syncFixes, or syncVariables)
2. Get the appropriate name array
3. Loop through names to create/update modifier objects
4. Call the shared processData1D() function for Data1D processing
5. Assign to the appropriate output collection
6. Clean up the name array (see issue fix: Memory leak in sync modifiers - missing cleanup of name arrays #183)