fix: clean up npm artifacts before web-bot-auth build

[rgarcia]

Summary

• Cleans up package-lock.json and node_modules before npm install to avoid npm optional dependency resolution bugs

Background

The npm install step can fail with optional dependency resolution issues. Removing these artifacts before install ensures a clean state.

Ref: npm/cli#4828

Test plan

• Run kernel extensions build-web-bot-auth --to ./test-output
• Verify the build completes successfully
• Upload the extension to a browser session and verify it loads

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Note

Improves reliability of web-bot-auth extension build.

• Before npm install, delete package-lock.json and node_modules in the extracted repo to avoid an npm optional dependency bug; adds informational logging
• No other functional changes to build steps or outputs

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