Improve skills-validator invoking and outputs presenting

[JanKrivanek]

Context

Fixing the skill-validator invocation to prevent invocation errors - e.g.:

• error about not found agents: https://github.com/fix(agents): remove invalid tool names across multiple agents 🤖🤖🤖 #1384#issuecomment-4234484880
• error about invocation parameters: https://github.com/Add Fabric Data Agent plugin — create, test, tune agents via MCP #1369#issuecomment-4221967641

• making the validation output .md structured (currently it's cli formatting)

---

By submitting this pull request, I confirm that my contribution abides by the Code of Conduct and will be licensed under the MIT License.

[Copilot]

Pull request overview

Updates the Skill Validator PR comment workflow to present validator output in a more structured, Markdown-friendly format and to reduce invocation/output-related noise when posting results back to pull requests.

Changes:

• Sanitizes captured validator output (handles missing output file and strips ANSI color codes).
• Replaces keyword-based finding counts with emoji-based counts (❌/⚠/ℹ) and adds structured summary tables.
• Adds a compact “Summary” section plus a <details> block containing the full validator output.

Show a summary per file

File	Description
.github/workflows/skill-check-comment.yml	Reformats the PR comment body with tables + summary extracted from validator output, and improves output handling/sanitization.

Copilot's findings

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

[Copilot]

summaryLines falls back to the first 10 non-empty lines when no emoji-prefixed findings are detected. Since skill-validator output can include headers/info lines (e.g., "## ") even when there are no findings, this can populate the “Finding” table with non-findings and prevent the “No findings…” message from ever showing. Consider only building the findings table from highlightedLines (emoji-prefixed lines), and when that list is empty (and exitCode === '0'), render the no-findings message instead of a fallback slice of arbitrary output.

Suggested change

	const summaryLines = highlightedLines.length > 0
	? highlightedLines.slice(0, 10)
	: output
	.split('\n')
	.map(line => line.trim())
	.filter(Boolean)
	.filter(line => !line.startsWith('###'))
	.slice(0, 10);
	const summaryLines = highlightedLines.slice(0, 10);