fix(lit): use cross-platform script for copy-spec to support Windows

[jeevanjoseph03]

Problem

The renderers/lit build script copy-spec relied on Unix-specific commands (mkdir -p and cp), causing the build to fail on Windows environments.

Solution

Replaced the shell command with a new cross-platform Node.js script scripts/copy-schemas.js that uses the fs module to securely copy the schema files.

Verification

• Verified that npm run copy-spec runs successfully on Windows 11.
• Verified that npm run build completes without errors.
• Confirmed that the Restaurant Finder demo now starts and runs correctly.