feat(railway): Railway provider

[sam-goodwin]

Closes #637

Adds the Railway cloud provider: full resource coverage, live integration tests, and an end-to-end example.

Resources

Project, Environment, Service, Function (Effect-native runtime — bundles your Effect program, ships it through Railway's build pipeline, exposes it on a public domain), Database (template-equivalent Postgres/MySQL/Redis/Mongo with volume), Variables, Volume, TcpProxy, ServiceDomain, CustomDomain, ProjectToken, Webhook — plus the DatabaseUrl and VolumeMount bindings.

const project = yield* Railway.Project("my-project");
const db = yield* Railway.Database("Postgres", { project, kind: "postgres" });

class Api extends Railway.Function<Api>()("Api", { project }, Effect.gen(function* () {
  const databaseUrl = yield* Railway.DatabaseUrl.bind(db);
  return { fetch: /* ... */ };
}).pipe(Effect.provide(Railway.DatabaseUrlLive))) {}

Typed errors via distilled

All provider error handling goes through typed @distilled.cloud/railway errors (EnvironmentNameConflict, ServiceNameConflict, ServiceNameInvalid, TcpProxyLimitExceeded, ProjectCreateRateLimited, ...) discovered by live testing and recorded as patches — no generic UnknownRailwayError handling anywhere. Submodule bump pairs with alchemy-run/distilled#340.

Reconciler notes

• Railway soft-deletes resources (deletedAt); read/observe treat soft-deleted as missing and name-conflict adoption skips them.
• Create adopts same-named orphans on EnvironmentNameConflict/ServiceNameConflict (service enumeration via a hand-written environment.serviceInstances query — Railway has no top-level list-services API).
• TcpProxy replaces delete-first (Railway allows one proxy per service instance) and treats TcpProxyOperationInProgress on an already-removed proxy as success.
• Railway rate-limits project creation to 1/30s per workspace (failed attempts re-arm the window), so tests share one persistent project and only Project.test.ts exercises the project lifecycle.

Example

examples/railway-postgres — Project + Database + Function wired through the DatabaseUrl binding; verified live (/, /health, and /db round-tripping a query through the bound Postgres) and destroyed.

Tests

All 11 Railway suites pass against the shared project (Project.test.ts excluded from the default run per rate limits). Tests are idempotent: create adopts orphans by name and every test tears down via Effect.ensuring(stack.destroy()).