Preserve server path prefixes when building URLs

[kriptoburak]

Summary

• preserve server path prefixes when building operation request URLs
• add a regression test for an absolute OpenAPI operation path with a base URL path
• fix new URL(path, baseUrl) incorrectly resolves paths when spec uses a relative server URL with a path prefix #1

Validation

• pnpm test
• pnpm test request-builder.test.ts
• pnpm build

Notes

• Frozen install is blocked because the existing lockfile is out of sync with package.json.
• pnpm lint is blocked because the Biome binary is not installed by the current dependencies.