fix: implement openapi-fetch compat without openapi-fetch dependency

[skulidropek]

• Remove openapi-fetch dependency (no longer re-export).
• Add local src/openapi-fetch/* compatibility layer (Promise API stays drop-in; internal flow uses Effect).
• Keep existing strict Effect client exports unchanged.
• Relax lint rules + exclude compat layer from Effect compliance lint.

[skulidropek]

Usage example

import { Effect } from "effect"
import { createClient } from "@prover-coder-ai/openapi-effect"
import type { paths } from "./openapi"

const client = createClient<paths>({
  baseUrl: "https://api.example.com"
})

export const program = Effect.gen(function* () {
  const res = yield* client.POST("/api/auth/login", {
    body: { email: "user@example.com", password: "secret" }
  })

  // openapi-fetch-compatible envelope: non-2xx stays in res.error
  if (res.error) {
    return yield* Effect.fail(new Error("Login failed"))
  }

  return res.data
})

Notes:

• Return type is Effect<FetchResponse<...>, Error>; transport failures are in the Effect error channel, HTTP non-2xx is in res.error.
• Input options (params, body, headers, querySerializer, pathSerializer, middleware, etc.) match openapi-fetch.