Worker routes (service-worker handlers) + worker redirect & bundle fixes

[siffogh]

Summary

Adds worker routes — the mirror of TanStack server routes, but the handlers run in the service worker. Declare them with the worker route option; the route's path is the identity (no name, no codegen — the router is the dispatch table). This lets a single stateful client (a local-first / sync-engine client like Zero or Replicache) live in the worker so reads and writes both go through it, and a hard-load WSR render reflects exactly what the user just did — one client, one store, no cross-client round-trip, no stale flash.

// src/routes/api/todos.ts
export const Route = createFileRoute("/api/todos")({
  worker: {
    handlers: {
      GET: async () => Response.json(await getClient().list()),
      POST: async ({ request }) => { await getClient().add(await request.json()); return new Response(null, { status: 204 }); },
    },
  },
  // optional: a `server` handler for the same method = the no-worker (SSR/first-load) fallback
});

Call them with workerFetch(path, init), which resolves in the right place:

• in the worker (a wsr loader on hard load) → runs the matched handler directly (a worker can't fetch itself);
• on the main thread (nav, event handlers) → fetches the path, which the worker intercepts;
• on the origin server (SSR, no worker) → 503, so the caller falls back (e.g. empty shell).

broadcastToClients(message) pushes invalidations to pages.

Supersedes the earlier createWorkerFn approach in this PR: routing by path drops the explicit name and needs no build-time transform — same ergonomics as server routes.

Also in here (fixes surfaced building on WSR)

• Honor thrown redirects. A redirect() thrown in beforeLoad/loader was captured on router state but never acted on, so the worker rendered the original route instead of redirecting (e.g. an auth gate → /login). renderRequest now returns a real redirect Response.
• Keep the dev worker under the SW script-size limit. The inline sourcemap ~doubled the bundle and could push it past Chromium's ~6 MB limit ("Failed to access storage"); the worker build no longer inlines a sourcemap.
• Single React/router copy in the worker bundle (resolved from the app root) so a duplicate instance can't make SSR hooks read null.

Tests & docs

• worker-fetch.test.ts (dispatch, request gating, the worker/main/server paths) and worker-redirect.test.ts. 47 tests passing.
• README: Worker routes section + API entry. Changeset included (minor).

(Branch name is feat/worker-functions for history reasons; the feature is worker routes.)