Provider configuration upgrades and session reliability

🚀 Improvements

• Improved Model Provider configuration flow and connection stability.
• Improved the OAuth-based Provider connection experience and show connected status.
• Added more preset provider options: DeepSeek / Kimi / MiniMax / SiliconFlow.
• Preset models now display context usage.
• Conversations now support dynamically switching output styles.

🔁 Changes

• Refactored Claude Code plugin session rebuild logic for consistency and reliability.
• Agents can now join @menu, making invocation more intuitive.
• Improved Command editing and parsing, with new usage hints.
• Providers now auto-activate available models after login.
• sub-agents management now reads uniformly from the Rust side.
• Session update notifications now include context usage information.

🐛 Fixes

• Fixed API key and Provider data desync.
• Fixed abnormal states in OAuth login flows on some environments.
• Fixed Providers not being selected or activated in some cases.
• Fixed Base URL, Gemini URL, and other config anomalies in some environments.
• Fixed connecting when the model is empty in some environments.
• Fixed Provider container styling and minimum height.
• Fixed chat history loss after upgrading.
• Fixed session cache not cleared after revert/rollback.
• Fixed session grouping errors when loading history.
• Fixed session load errors after plugin setting changes in some environments.
• Fixed Git status display on non-ASCII paths.
• Fixed file tree snapshot comparison failing on some pages.
• Fixed MCP Server errors caused by overly long environment variables.
• Fixed path-related issues.