[1/2] LT-22324: add FieldWorks UI automation support

[johnml1135]

Summary

This PR keeps only the support-side additions that are independent of the render cleanup branch: FieldWorks live-app automation guidance, screenshot evidence workflow notes, and WinForms MCP setup for UIA2 automation with WinApp/UIA3 fallback guidance.

Stack

• Part 1 of 2
• Merge this PR first
• Follow-up stacked PR: [2/2] Move agent skills to .agents #873

Included

• Add a FieldWorks WinForms/WinApp automation skill under .github/skills/fieldworks-winapp.
• Add a Windows-focused screenshot capture skill under .github/skills/smart-screenshot-capture.
• Add winforms-mcp to .vscode/mcp.json with headless net48 settings.
• Document WinForms MCP/UIA2 and WinApp/UIA3 fallback usage in Docs/mcp.md.

Excluded

• Render benchmark infrastructure, render baselines, native render/cache changes, and OpenSpec render-speedup artifacts.
• Skill relocation to .agents/skills, which is split into a separate stacked PR.
• LT-22324 font-option implementation behavior.

Verification

• git diff --name-status cleanup/non-render-pr-split...HEAD
• git diff --check cleanup/non-render-pr-split...HEAD
• python -m json.tool .vscode/mcp.json
• git grep -n "LT-22324" -- .github/skills/fieldworks-winapp returned no matches

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[jasonleenaylor]

Build/Agent/fix-whitespace.ps1 line 13 at r1 (raw file):

}

function Test-HasUtf8Bom {

Was removing this intentional? It seemed this would produce less churn in the repo with it in.

[johnml1135]

Good catch. That removal wasn't intentional. I restored the BOM-preserving behavior in Build/Agent/fix-whitespace.ps1 so the whitespace fixer keeps existing UTF-8 BOMs and avoids unnecessary churn. The fix is on the branch now in 47111a3.