Slim @augur/core: drop hosted-provider classes

[willgitdata]

Summary

Smaller, lighter, easier-to-grok `@augur/core` for OSS launch. Hosted providers are a 30-line interface implementation away — shipping them in core was decision paralysis ("which embedder?", "is OpenAIEmbedder maintained?") more than help.

What's removed

Class	Why removed
`GeminiEmbedder`	Fetch wrapper around `gemini-embedding-001` (~230 lines). Users with API keys are better served by `@google/generative-ai` directly.
`OpenAIEmbedder`	60-line fetch wrapper around `POST /v1/embeddings`. Idiomatic users use the `openai` SDK; we drift with each API change.
`CohereReranker`	50-line fetch wrapper around Cohere rerank. Use `cohere-ai` SDK.
`JinaReranker`	50-line fetch wrapper around Jina rerank. Use `jinaai` SDK or fetch direct.
Helpers (`sleep`, `parseRetryAfter`)	Only used by GeminiEmbedder.

Plus 6 fetch-mock test cases that go with them.

Total: ~390 lines + 11 tests removed. Net diff: −713 / +83.

What stays in core

Offline-only (zero network at runtime):

• Embedders: `HashEmbedder` (placeholder), `TfIdfEmbedder` (real IR baseline, no deps), `LocalEmbedder` (semantic embeddings via on-device ONNX, opt-in transformers.js dep)
• Rerankers: `HeuristicReranker`, `LocalReranker` (cross-encoder ONNX), `MMRReranker` (diversity), `CascadedReranker` (chain pipelines)
• Adapters: `InMemoryAdapter`, `PineconeAdapter`, `TurbopufferAdapter`, `PgVectorAdapter` (these `fetch` wrappers stay because each is genuinely thin and the providers' SDKs are heavier than warranted)
• Chunkers: Fixed/Sentence/Semantic + Metadata/Doc2Query wrappers
• Routing + traces unchanged

Hosted-provider migration path

EXAMPLES.md §5 now shows users writing their own `Embedder` / `Reranker` against the official SDK:

```ts
import OpenAI from "openai";
import { Augur, type Embedder } from "@augur/core";

class OpenAIEmbedder implements Embedder {
readonly name = "openai:text-embedding-3-small";
readonly dimension = 1536;
private client = new OpenAI();
async embed(texts: string[]): Promise<number[][]> {
const r = await this.client.embeddings.create({
model: "text-embedding-3-small",
input: texts,
});
return r.data.map((d) => d.embedding);
}
}
```

Same number of lines as our deleted class; uses the maintained, idiomatic SDK instead of our reimplementation that drifted with each API change.

Server CLI changes

`AUGUR_EMBEDDER` values:

• `"openai"` → no longer recognized (use `hash`/`tfidf`/`local`, or pass a custom embedder via your own server build)
• `"tfidf"` → `TfIdfEmbedder` (newly wired, was missing)
• `"local"` → `LocalEmbedder` (newly wired)
• `"hash"` → unchanged
• `AUGUR_LOCAL_MODEL` env var lets you override the default ONNX model

Verification

• `pnpm -r build` clean (core + server)
• `pnpm typecheck` clean (core, server, dashboard, evaluations)
• `pnpm --filter @augur/core test` — 91/91 pass (was 102; -11 hosted-provider tests removed)
• `pnpm --filter @augur/evaluations test` — 12/12 pass

🤖 Generated with Claude Code