fix(TRAC-1339): throw ValidationError for non-string input in urlParse and stripProtocol

[mfaris9]

Jira: TRAC-1339 (LTRAC-1395)

What? Why?

• urlParse and stripProtocol passed input straight to url.parse(), so an undefined theme variable threw a raw TypeError and 500'd the whole page render
• Both helpers now throw ValidationError for non-string input, which the renderer preserves (fix(TRAC-875): preserve ValidationError type in render/renderString #404) so it can surface as a 4xx template error pointing at the theme instead of a 500
• Same pattern as strReplace and encodeHtmlEntities

How was it tested?

• Added specs asserting both helpers throw ValidationError for undefined, number, and object input
• npm test passes (890 tests), coverage 97.66%
• npm run lint clean
• Tested in stencil-cli: "Non-string passed to urlParse : Error: Non-string passed to urlParse"

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cc @bigcommerce/storefront-team

🤖 Generated with Claude Code

[github-actions]

🎉 This PR is included in version 6.6.4 🎉

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• npm package (@latest dist-tag)
• v6.6.4

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