The skills/agents check filters-in only touched files

[JanKrivanek]

#13537 followup

Context

The PR above introduced skills/agents files checking within PRs touching skills/agents
But it checked all the files - possibly repeating same and unactionable findings

Changes Made

We now filter only for the touched skills and agent files

[github-actions]

🔍 Skill Validator Results

✅ All checks passed

Scope	Checked
Skills	13
Agents	1
Total	14
Severity	Count
---	---:
❌ Errors	0
⚠️ Warnings	0
ℹ️ Advisories	0

Summary

No findings were emitted by the validator.

Full validator output

```text No validator output captured. ```

[Copilot]

Pull request overview

Updates the Skill Validation GitHub Actions workflow to scope skill-validator checks to only the skills/agents modified in a pull request, reducing redundant and unactionable findings.

Changes:

• Add a PR-only step that queries the PR file list and identifies changed .github/skills/** and .github/agents/** paths.
• Remove unchanged skill directories / agent files from the workspace before running skill-validator.
• Skip the skill-validator step on PRs where no skill/agent files changed, and normalize the recorded exit code when the check is skipped.

Show a summary per file

File	Description
.github/workflows/skill-validation.yml	Detects PR-changed skill/agent files, filters the workspace to only those paths, and conditionally runs skill-validator.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 4