feat(typescript): export an operationId-keyed Operations index type for types-only consumers

[kdumontnu]

Description

Split out of #4316 (its "Ask 2") so each request can be tracked and reviewed on its own.

Context is the same as #4316: we use @hey-api/openapi-ts with only the @hey-api/typescript plugin and our own HTTP client. The generated per-operation types (PostPingData, PostPingResponses, …) are exactly what we build on, but there is no generated way to enumerate them.

Ask: export a single type keyed by operation ID that references each operation's types:

export type Operations = {
    postPing: { data: PostPingData; responses: PostPingResponses; errors: PostPingErrors };
    // …
};

Why it's needed

Today a types-only consumer who wants a generic typed wrapper has to hand-maintain the map above. The compiler catches stale names and missing entries, but pairing a key with a different operation's types compiles silently — postPing: { data: GetPingData } is a valid object type. That miswiring only surfaces at runtime.

A generated index is correct by construction and stays in sync as the spec evolves. It enables:

• one generic call site with full per-endpoint inference: call<K extends keyof Operations>(id: K, data: Operations[K]['data'])
• exhaustive mapped types over all operations (handler tables, mock registries) that fail to compile when the spec adds an operation

This is specifically for types-only consumers — SDK-plugin users already get per-operation functions.

Reproducible example or configuration

export default defineConfig({
    input: './openapi.json',
    output: './src/generated',
    plugins: ['@hey-api/typescript'],
});

System information (optional)

@hey-api/openapi-ts 0.99.0, types-only, Node 26 / pnpm 11.

[pullfrog]

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