♻️ Make the url a site reads itself as a context api

[taras]

Motivation

The site builds absolute urls in four places — the sitemap, the blog feed,
llms.txt, and every page's canonical link — and each one derived its origin by
reaching for the request through useAbsoluteUrlFactory, a helper parked in the
current-request plugin.

That left no seam. What a document advertises was fixed by whatever served it,
and the one url that names production, the canonical link, was a string literal
inside a JSX layout component. A plugin module is middleware; it should not also
be where url logic lives.

Approach

www/context/url.ts is an api built with createApi, alongside fetch,
process and logger:

export interface UrlApi {
  url(path: string): Operation<string>;
  canonical(options: { base: string }): Operation<string>;
}

export const { url, canonical } = urlApi.operations;

urlApi.around can now rebase either, and because url resolves one path at a
time rather than handing back a builder, middleware sees each path and can
rewrite some while leaving others alone.

The call sites that consumed the old builder synchronously move to all(): the
sitemap's entries, the feed's items, and the package list in llms.txt.
plugins/current-request.ts is left holding only its plugin.

Tests

This is a pure refactor, so the check is that nothing it produces changed. I
booted the site on this branch and on its base and diffed the documents:

IDENTICAL  llms.txt
IDENTICAL  sitemap.xml
IDENTICAL  canonical link
DIFFERS    blog/feed.xml   <lastBuildDate> only, which is new Date()

deno fmt, deno lint, deno check clean; the unit suite passes.

Stack

This sits on #1248 and is a prerequisite for #1247, which was carrying it:

#1245  tm/agents-contract
#1248  tm/staticalize-base
       tm/url-api            ← this
#1247  tm/markdown-routes

Based on tm/staticalize-base so the diff shows only its own six files; GitHub
retargets it to v4 when #1248 merges.

[github-actions]

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Effection

Effection is a structured concurrency and effects framework for JavaScript.

Effection

Effection is a structured concurrency and effects framework for JavaScript.