document.readyState was hardcoded to "complete" so scripts checking
readyState === 'loading' always took the wrong branch. Fixed by using a
JS global (__documentReadyState__) that Rust sets to "loading" before
any scripts execute, "interactive" before DOMContentLoaded fires, and
"complete" after load.
document.addEventListener and document.dispatchEvent on Document were
no-ops, so DOMContentLoaded listeners registered by inline scripts were
never called. Added proper listener storage and dispatch on Document.
Adds document.getElementsByName() (was missing entirely).
Page.reload is now implemented (re-navigates to the current URL),
resolving "Unknown Page method: reload" errors from Playwright.
data: URL navigation now works, fixing Playwright's goto("data:text/html,...")
pattern that previously errored with "invalid format".
Page.navigate logic extracted into do_navigate() so reload can reuse it.
Fixes#137, #146 (SPA bootstrap lifecycle ordering).