Provide Request instance in onSkippedRequest callback #3801

The onSkippedRequest callback currently receives only the URL string and a reason:

// packages/core/src/enqueue_links/shared.ts
export type SkippedRequestCallback = (args: { url: string; reason: SkippedRequestReason }) => Awaitable<void>;

This means handlers can't access request metadata (notably userData) for skipped requests. In several call-sites the full Request is already available but gets discarded — e.g. in basic-crawler.ts the robots.txt skip has the whole request object yet forwards only request.url, and the limit skip explicitly extracts request.url! before calling handleSkippedRequest.

Proposal

Pass the full Request to the callback instead of the URL string:

export type SkippedRequestCallback = (args: { request: Request; reason: SkippedRequestReason }) => Awaitable<void>;

url is dropped, since it's just request.url. To guarantee a Request is always available, normalize skipped URLs to Request at the choke points (the enqueue path and both extractLinks implementations), the same way the Python PR does. Then thread the Request through the basic-crawler.ts call-sites where it's already available instead of dropping it.

Breaking change

This changes the callback signature, so it lands in the next major (v4). We're intentionally not keeping it backward compatible.

Context

Python parity. This was originally proposed for crawlee-python as a backward-compatible change that dual-dispatched on the type annotation of the callback's first parameter (apify/crawlee-python#1999): annotate it as Request to receive the object, or as str (or leave it unannotated) to keep receiving the URL string.

During review we dropped that approach. The runtime annotation inspection is fragile (for instance, it fails to match when the annotation uses a TYPE_CHECKING import alias), so we decided to do it as a clean breaking change in the next major instead. Tracked for Python in apify/crawlee-python#2007.

For crawlee (JS) we follow the same decision: a clean breaking change, no dual dispatch and no optional request field.