fix channel quota and ark inference

[ErlichLiu]

Summary

• infer Volcengine Ark Anthropic-compatible URLs as ark-coding-plan for channel testing/model loading
• allow Zhipu Coding Plan Team quota checks to work with token-only credentials, while preserving optional org/project headers
• add focused channel-manager regression coverage for both paths

Root Cause

The plan quota UI treats Zhipu team organization/project IDs as optional, but the main-process quota path rejected token-only credentials before making the request. Separately, generic Anthropic-compatible Ark URLs were not routed to the built-in Ark Coding Plan branch, so model loading could attempt the unsupported generic /models path.

Validation

• bun test apps/electron/src/main/lib/channel-manager.test.ts apps/electron/src/main/lib/agent-sdk-auth-env.test.ts packages/core/src/providers/anthropic-adapter.test.ts packages/core/src/providers/url-utils.test.ts packages/shared/src/utils/context-window.test.ts apps/electron/src/main/lib/agent-workspace-manager.test.ts apps/electron/src/renderer/lib/markdown-rich-text.test.ts
• bun run --cwd apps/electron typecheck
• git diff --check