capture browser console messages and uncaught page errors in puppeteer tests

Steps

1. register page.on('console', msg => { ... }) before navigating, so messages logged during page load are also captured
2. call msg.text() to get the human-readable log text, and msg.args() to access underlying JSHandles for structured logged objects
3. register page.on('pageerror', err => { ... }) to capture uncaught exceptions thrown in the page context, separate from console.error calls
4. assert in the test that no unexpected 'error'-type console messages or pageerror events occurred during the flow
5. collect messages into an array across the whole test and flush/report them at the end rather than asserting on each event individually