feat(provider): add Atlas Cloud preset

[binyangzhu000-sudo]

Summary

• add Atlas Cloud as an OpenAI-compatible model provider preset
• preconfigure https://api.atlascloud.ai/v1 with qwen/qwen3.5-flash and deepseek-ai/deepseek-v4-pro
• include focused coverage for preset creation and Kun runtime provider resolution

Validation

• npm ci --ignore-scripts
• npm run build:extensions
• npm exec -- vitest run src/shared/app-settings-provider.test.ts
• npm exec -- eslint src/shared/model-provider-presets.ts src/shared/app-settings-provider.test.ts
• npm exec -- tsc --noEmit -p tsconfig.web.json
• git diff --check
• Atlas Cloud live /v1/models returned 120 models and confirmed qwen/qwen3.5-flash and deepseek-ai/deepseek-v4-pro

Note: npm exec -- tsc --noEmit -p tsconfig.node.json currently still reports unrelated existing missing/type issues around extension/design dependencies such as @xmldom/xmldom, safe-regex2, and semver.

No README changes.

[XingYu-Zhong]

可以使用自定义api