fix(sitemap): remove getProvider() fan-out — pre-filter slugs in worker

[Flotapponnier]

Problem

After the slim-blob sitemap shipped, buildFullSitemap() called getProvider(slug) 505 times in parallel to validate provider slugs. Each call internally triggers loadAggregateFromBlob() which cannot be cached (>2MB unstable_cache limit), so each of the 505 calls fetched the 4.25MB blob independently — OOM crash in ~65s, bypassing both the 75s JS timeout and the route handler try/catch.

Fix

Worker (publish-aggregate.ts): pre-filter providerSlugs at publish time to exclude chain slugs, HL builder slugs, perp venue slugs (except polymarket), and removed slugs. These are O(1) set lookups using shared constants.

Vercel (sitemap-builder.ts): replace the Promise.all(getProvider()) async fan-out with a sync .filter() using the same set checks (safety net). Remove the dead getProvider import. COMPARE_PAIRS routes are also emitted directly (curated list, no validation needed).

Result: buildFullSitemap() makes zero async provider calls — fetches only the 50KB slim blob + answers + alternatives (~15ms total).