Fix HTTPFacilitatorClient not following 308 redirects

[ayushozha]

Summary

Fixes #1692

The x402.org/facilitator/supported endpoint returns HTTP 308 before resolving to 200. HTTPFacilitatorClient did not normalize the base URL or explicitly request redirect following, causing syncFacilitatorOnStart to silently fail in some JS runtimes. When no supported payment kinds are loaded, the middleware passes all requests through as 200 instead of returning 402.

Root cause

$ curl -s "https://x402.org/facilitator/supported" -w "\n%{http_code}" -o /dev/null
308

$ curl -sL "https://x402.org/facilitator/supported" -w "\n%{http_code}" -o /dev/null
200

While the Fetch API default redirect mode is "follow", not all JS runtimes (Node.js versions, edge runtimes, polyfills) handle 308 redirects consistently — especially for POST requests where method preservation is required by spec but not always implemented.

Changes

File	Change
typescript/packages/core/src/http/httpFacilitatorClient.ts	Strip trailing slashes from URL in constructor; add redirect: "follow" to all fetch calls
typescript/packages/core/test/unit/http/httpFacilitatorClient.test.ts	Add URL normalization tests + redirect option propagation tests
typescript/.changeset/fix-facilitator-redirect.md	Changeset fragment

Test plan

• URL normalization: trailing slash stripped, multiple slashes stripped, clean URL unchanged, default URL correct
• Redirect option: redirect: "follow" passed on getSupported(), verify(), settle()
• Endpoint URL construction correct after normalization
• All 15 tests pass (7 existing + 8 new)

cc @CarsonRoscoe @andichen0420

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