fix(demohouse/skill-validation): accept CRLF frontmatter

[dajiaohuang]

Summary

• allow the car decision assistant skill validator to read CRLF frontmatter
• apply the same line-ending handling to the sales intelligence workbench validator
• preserve the existing LF-only behavior while making native validation portable to Windows checkouts

Fixes #258.

Verification

• npm run release:verify in demohouse/car-decision-assistant (lint, typecheck, build, 115 tests, release validation, skill validation, isolated installer test)
• npm run release:validate in demohouse/sales-intelligence-workbench
• npm run skill:validate in demohouse/sales-intelligence-workbench
• byte-level regression check against both LF Git blobs and CRLF working-tree files
• git diff --check

The broader sales backend verifier remains blocked on this Windows/Node.js 24 environment by its existing spawnSync npm.cmd EINVAL behavior; it reaches that step only after the patched skill validation passes.