fix(specs): show correct host for MX endpoints in merged API reference

[walletconnect-agent]

Problem

scripts/generate-specs.mjs merges the Core and MX OpenAPI specs into one document but sets only a document-level server pointing at Core (api.pay.walletconnect.com). MX-sourced endpoints inherit it, so the docs page + playground show the wrong host for merchant-API endpoints.

Fix

When merging, stamp each operation with its source service's server (servers: [{ url }]) — Core ops get the Core host, MX ops get api.merchant.pay.walletconnect.com. Mintlify respects per-operation servers. Only real HTTP-method keys are stamped, and any pre-existing operation servers is preserved.

Follow-up (not in this PR)

The committed snapshot (api/2026-02-18.json + api-reference/ MDX) is regenerated by fetching the live service specs, which only runs via the manual Update OpenAPI Specs workflow (workflow_dispatch). A maintainer needs to re-run it to (a) apply this per-service-server fix to the output and (b) refresh the stale snapshot (e.g. add Core's /v1/payments/{id}/transition, drop the phantom GET /v1/payments). Consider adding a schedule/trigger so it stops drifting.

Thread: https://reown-inc.slack.com/archives/C0A1N1Q7XS8/p1783931638893429

[walletconnect-agent]

Closing/abandoning this — confirmed in thread that MX endpoints are already routed under api.pay.walletconnect.com (unified gateway). So the merged spec's single api.pay server is correct, and stamping the api.merchant.pay host per-operation would point the playground at a host that isn't the canonical one. No base-URL change needed.

The real remaining issue is snapshot staleness (phantom GET /v1/payments, missing /v1/payments/{id}/transition), fixed by re-running the manual Update OpenAPI Specs workflow — not by this change. Please close this PR.