Add a new Volcengine (Volcano Engine Ark) provider for accessing
DeepSeek-V4-Pro and DeepSeek-V4-Flash via the Volcengine Coding API.
Changes:
- Add ProviderKind::Volcengine to config crate with default base_url
pointing to Volcengine Coding API (api/coding/v3)
- Add DeepSeek-V4-Pro and DeepSeek-V4-Flash models to the agent
model registry under Volcengine provider
- Add ApiProvider::Volcengine to TUI with full picker/dropdown support
- Wire up CLI --provider, config get/set/unset, and secrets resolution
- Add environment variable aliases: VOLCENGINE_API_KEY, ARK_API_KEY
- Ignore local dev scripts (*.cmd, backup/)
dzyuan8
45b04c4444