feat(llm): add Atlas Cloud provider

[binyangzhu000-sudo]

What this adds

atlascloud as an LLM provider for the Atlas Cloud gateway, following the cheaperinference / requesty shape — a 21-line module pointing ChatOpenAI at https://api.atlascloud.ai/v1:

Env var	Default
ATLASCLOUD_API_KEY	''
ATLASCLOUD_MODEL	deepseek-ai/DeepSeek-V3.1-Terminus
ATLASCLOUD_BASE_URL	https://api.atlascloud.ai/v1

Disclosure: I work at Atlas Cloud. The model catalog at https://api.atlascloud.ai/v1/models is public and needs no key.

Embeddings

makeEmbeddings falls back to the OpenAI settings, and there is a comment saying why: Atlas Cloud serves chat completions only — POST /v1/embeddings returns 404 page not found, which I checked rather than assumed. That is the same thing cheaperinference.ts does, and .env.example notes it next to the key.

Testing

Provider tests: 6 files / 38 tests → 7 files / 42 tests, no failures. The new __tests__/atlascloud.test.ts mirrors cheaperinference.test.ts and adds one case for temperature / max-token pass-through.

$ npx vitest run backend/src/utils/llm/models/__tests__
baseline  Test Files  6 passed | 1 skipped (7)      Tests  38 passed | 3 skipped (41)
after     Test Files  7 passed | 1 skipped (8)      Tests  42 passed | 3 skipped (45)

$ npx vitest run              # whole suite
Test Files  8 passed | 1 skipped (9)   Tests  45 passed | 3 skipped (48)

$ npx tsc -p backend/tsconfig.json --noEmit
(clean)

Live round trip through the real provider and config, not a mock:

config.atlascloud_model = deepseek-ai/DeepSeek-V3.1-Terminus
config.atlascloud_base  = https://api.atlascloud.ai/v1

makeLLM(config).invoke(...)                              -> PageLM via Atlas Cloud OK
makeLLM({...config, atlascloud_model: 'zai-org/glm-4.7'}) -> 你好，世界。

The second call also shows ATLASCLOUD_MODEL switching models on the same key, which is the point of the gateway.

Files

backend/src/utils/llm/models/atlascloud.ts (new) · __tests__/atlascloud.test.ts (new) · models/index.ts (import + case) · config/env.ts (3 keys) · .env.example (provider list + its own section) · README.md (supported models line)

package-lock.json is deliberately not in the diff — npm install touched it locally, but nothing in this change adds a dependency.

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