Add Atlas Cloud well-known provider

[binyangzhu000-sudo]

Summary

• add Atlas Cloud to the well-known provider list as an OpenAI Chat Completions-compatible provider
• enable the existing official model auto-fetch flow so model IDs come from /v1/models after the user configures an API key

Validation

• verified https://api.atlascloud.ai/v1/models returns a standard data[].id/name model list with API-key auth
• self-reviewed the diff; this PR only changes src/well-known/providers.ts

No README, sponsor, logo, credits, or partner text changes.

[smallmain]

Thanks for your PR. Please resolve the conflicts, and I will merge it.

[binyangzhu000-sudo]

Thanks for the review. I pushed follow-up commit d2c85abd394c7e8d1f3c34bf606cc619cefcfed8 resolving the conflict with current main.

What changed:

• merged the latest main into the PR branch
• resolved src/well-known/providers.ts by keeping the Atlas Cloud provider entry and the upstream Kilo Code provider entry
• confirmed the PR diff against main is still limited to the Atlas Cloud provider entry

Validation:

• npm ci
• npm run compile
• npx vitest run test/unit/plan4-provider-catalog.test.ts test/unit/claude-opus-5.test.ts
• git diff --check origin/main...HEAD

Notes:

• No paid Atlas live POST was run; this is provider catalog wiring only.