feat: add Volcengine Agent Plan provider with 13 models

[AkariSam]

Summary

Add the Volcengine Agent Plan provider — a subscription-based AI service with 13 models accessible via an OpenAI-compatible endpoint.

Changes

• providers/volcengine-agent-plan/provider.toml — Provider metadata
• providers/volcengine-agent-plan/models/ — 13 model definitions

Proprietary models (standalone definitions)

Model	Context	Modalities	Reasoning
ark-code-latest	256K	text, image → text	toggle
glm-latest	1M	text → text	effort (high, max)
doubao-seed-2.0-code	256K	text, image → text	no
doubao-seed-2.0-pro	256K	text, image → text	effort (low, medium, high)
doubao-seed-2.0-lite	256K	text, image → text	effort (low, medium, high)
doubao-seed-2.0-mini	256K	text, image → text	effort (low, medium, high)

Third-party models (inherit upstream metadata via base_model)

Model	Base	Context	Modalities	Reasoning
glm-5.2	zhipuai/glm-5.2	1M	text → text	effort (high, max)
deepseek-v4-flash	deepseek/deepseek-v4-flash	1M	text → text	toggle + effort (high, max)
deepseek-v4-pro	deepseek/deepseek-v4-pro	1M	text → text	toggle + effort (high, max)
minimax-m2.7	minimax/MiniMax-M2.7	200K	text → text	toggle
minimax-m3	minimax/MiniMax-M3	512K	text, image → text	toggle
kimi-k2.6	moonshotai/kimi-k2.6	256K	text, image → text	toggle
kimi-k2.7-code	moonshotai/kimi-k2.7-code	256K	text → text	toggle + budget_tokens

Notes

• All costs are 0 (subscription-based, same pattern as Alibaba Coding Plan)
• kimi-k2.6 uses base_model_omit = ["video"] since Volcengine does not support video input for this model
• The provider uses @ai-sdk/openai-compatible with endpoint https://ark.cn-beijing.volces.com/api/plan/v3

[rekram1-node]

why are u editing the gitignore

[AkariSam]

why are u editing the gitignore

sorry for including the .gitignore file.