bugfix: handle negative deductions returned by evaluator

[JellyPork]

Closes #24

Summary

Fix a crash in resume evaluation when the model returns a negative value for deductions.total.

The evaluator expects deductions to be stored as a positive magnitude and applied later as a subtraction. In some runs, the model returns values like -10, which causes EvaluationData validation to fail and stops the scoring flow.

Changes

• normalize deductions.total to a positive number during validation
• clarify the prompt contract so deductions are returned as magnitude-only values
• add a regression test covering the negative-deductions case

Repro

An evaluator response like this can cause the run to fail:

"deductions": {
  "total": -10,
  "reasons": "Broken or inactive links"
}

Prompt change examples

Before:

"deductions": {
  "total": -10,
  "reasons": "Broken or inactive links"
}

After:

"deductions": {
  "total": 10,
  "reasons": "Broken or inactive links"
}