[Infra] Check for overfit in the scenario prompt as well

[JanKrivanek]

Motivation

Revealing the need to use skill (specific on or in general) in scenario prompt is a sign of overfitting as well.
Previously we've been checking anly the rubric graders

[Copilot]

Pull request overview

Adds prompt-level overfitting detection to the skill validator so scenario prompts that explicitly reference (or instruct using) a skill are treated as overfitting signals, alongside existing rubric/assertion checks.

Changes:

• Extend overfitting schema/model to include prompt_assessments and incorporate them into score computation.
• Add deterministic prompt scanning (DetectPromptOverfitting) and merge it with LLM-provided prompt assessments.
• Update console reporting, dashboard data generation, and expand test coverage for prompt overfitting.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
eng/skill-validator/src/Services/OverfittingJudge.cs	Adds deterministic prompt checks, parses/merges prompt_assessments, and updates scoring + LLM prompts/schema.
eng/skill-validator/src/Models/Models.cs	Introduces PromptOverfitAssessment and adds PromptAssessments to OverfittingResult.
eng/skill-validator/src/Services/Reporter.cs	Prints prompt-level overfitting signals in console output for moderate/high results.
eng/dashboard/generate-benchmark-data.ps1	Flags scenario overfitting when prompt assessments exist (supports new schema).
eng/skill-validator/tests/OverfittingJudgeTests.cs	Adds coverage for prompt detection, parsing, and score effects; updates existing constructions for new result shape.

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