[codex] Centralize provider capability matching

[Wangnov]

Summary

#64 and #65 are now merged into main, and this branch has been rebased on top of the updated main. The PR diff is now the follow-up architecture refactor only.

• Adds utils::provider_profiles as the shared home for provider endpoint currency rules, model currency fallbacks, model-name extraction, and context-window matching.
• Wires usage currency detection to the shared provider helpers while preserving the existing auto-detection priority.
• Wires token context-window resolution and config defaults to the same shared provider profile table.
• Moves shared matching tests into the provider profile module, including MiniMax, DeepSeek, Kimi/Moonshot, Qwen/DashScope, Volcengine, GLM, Tencent, and Xiaomi MiMo coverage.

Refs #63, #64, #65.

Validation

• make ci