feat(script): register the WHATWG URL and text-encoding globals

[pathscale]

boa_runtime implements URL, TextEncoder and TextDecoder, and nothing registered them. Only Console was, so a page received a JavaScript engine with a console and no web platform around it.

The failure does not look like a missing global

@solidjs/router constructs a URL while its module is evaluating. So a router-based application does not break when you navigate — it throws before the first component renders. What you see is a blank page and one line in the log naming the entry chunk, which is why this survived so long.

Found while trying to run fleet sites under qa-inspect-host: none of them could boot.

The change

Registered per extension rather than through boa_runtime::register, which would also install its own setTimeout/setInterval over the ones in timers.rs that are wired to this document's event loop.

Tests

Four, in packages/blitz-script/tests/whatwg_url.rs. Each reads a parsed field rather than checking that a constructor exists, because a constructor that exists and returns a bare object would satisfy the weaker test:

• component parsing, including a non-default port and a fragment
• relative resolution against a base (../c against /a/b/d), the half a naive stub gets wrong
• an invalid URL throws, asserted by error name — new URL("/x") throws whether the constructor is missing or the string is bad, so "it threw" alone would pass against no URL at all
• TextEncoder round-trips a non-ASCII character, where a byte-per-char stub diverges

With the registration removed, three of the four fail.

Still missing

This does not finish the job. URLSearchParams is absent and boa_runtime's own URL.searchParams throws "not implemented", so a router still cannot boot. Also absent, measured by probe page: matchMedia, fetch/Headers/Request/Response, MutationObserver, ResizeObserver, IntersectionObserver, AbortController, DOMParser, Blob, FormData, localStorage, sessionStorage; document.getElementsByTagName, createTreeWalker, createRange, adoptNode, evaluate; and insertAdjacentHTML, attachShadow, scrollIntoView, animate on elements.

URLSearchParams is the next blocker and belongs in the ps-boa fork rather than here.

[pathscale]

Folded into #89. The commit is cherry-picked there and its four tests pass on that branch. One branch for the series means one 0.4.x release rather than two.