feat(polar): add Effect-native SDK for the Polar billing API

[Butch78]

Adds @distilled.cloud/polar, an Effect-native client for Polar's billing API — products, subscriptions, customers, meters, events, checkouts, benefits, discounts — generated from the Polar OpenAPI 3.1 spec via the shared sdk-core generator, with exhaustive error typing, retry policies, and Bearer PAT/OAT credentials.

The first commit is a general fix to the OpenAPI generator that Polar's spec surfaced; the second is the package.

Generator fix (commit 1)

The operation generator only read .properties off a request body, so two shapes degenerated to an empty input schema — the op compiled but could never send a body:

• Top-level oneOf/anyOf bodies (discriminated unions like CustomerCreate / ProductCreate) → now flattened into one struct (union of branch properties; required only where required in every branch).
• Chained $ref bodies (CheckoutCreate → $ref CheckoutProductsCreate) → now resolved in a cycle-guarded loop.

Strictly additive — bodies that already had .properties are untouched, so no existing package's generated code changes. On Polar this took empty create bodies from 17 down to 6 (the remaining 6 are genuinely body-less GETs).

- const created = yield* customerscreate({})            // empty body — broken
+ const created = yield* customerscreate({ email, name }) // typed body

The package (commit 2)

• 186 operations generated from specs/openapi.json.
• Polar-tuned client: FastAPI { error, detail } / 422-validation error matching, sandbox vs production base URLs via POLAR_SERVER, and a layer({ accessToken, server }) builder alongside CredentialsFromEnv.
• Sandbox-guarded nuke.ts (refuses production without --allow-production; --dry-run; nuke-config.json exclusions).
• Live tests (customer create/get/delete lifecycle + organizations read/auth) gated on POLAR_ACCESS_TOKEN; they skip cleanly without it.
• Registered in root tsconfig.json, README.md, AGENTS.md, CI (ci-polar), and the website.

import * as Effect from "effect/Effect";
import * as FetchHttpClient from "effect/unstable/http/FetchHttpClient";
import * as Polar from "@distilled.cloud/polar";

const program = Polar.organizationslist({ limit: 20 }).pipe(
  Effect.provide(Polar.CredentialsFromEnv),
  Effect.provide(FetchHttpClient.layer),
);

Notes / divergences from the standard flow

• Built with the deterministic generateFromOpenAPI generator directly rather than create-sdk-full (which drives an interactive Opus session), so the operation naming follows the spec's operationIds verbatim.
• The spec is vendored at packages/polar/specs/openapi.json with specs:update as a curl refresh, instead of the usual distilled-spec-* submodule mirror (no org mirror repo exists yet — happy to switch to a submodule if you provision one).
• The website card uses a placeholder polar.svg — swap it for Polar's official brand asset before shipping the site.