#10266: feat(provider/modelscope): support modelscope provider

# Description This PR primarily adds support for the ModelScope API. Users can use community-supported models by providing a ModelScope API key. # For API-Key To obtain the ModelScope API-key, please refer to [this link](https://modelscope.cn/docs/model-service/API-Inference/intro). Please bind your [Alibaba Cloud account](https://modelscope.cn/docs/accounts/aliyun-binding-and-authorization) before use. <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> - Adds a new `modelscope` provider (OpenAI-compatible) with a default model and base URL, plus implicit provider injection when a ModelScope key is available. - Extends the onboarding/auth-choice flows (interactive + non-interactive) to accept/store `MODELSCOPE_API_KEY` and configure default model/provider settings. - Updates provider usage plumbing and docs to surface ModelScope as a supported provider. <h3>Confidence Score: 2/5</h3> - This PR is not safe to merge as-is due to auth wiring bugs that will break ModelScope usage in common paths. - Two issues appear to be definite functional bugs: implicit provider injection uses the env var name instead of its value, and the interactive onboarding path ignores the new `--modelscope-api-key` flag, causing prompting/misconfiguration. The rest of the changes are largely additive and consistent with existing patterns. - src/agents/models-config.providers.ts, src/commands/auth-choice.apply.api-providers.ts <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->