feat: show warning for unrecommended model selected in agent mode

[uinstinct]

Description

Show a warning below the text box when an unrecommended model is selected for agent mode.

• Model being suitable for agent mode is decided using the llm-info's recommendedFor field
• A "Know more" link to the issue points to https://docs.continue.dev/agent/model-setup
• Once the warning is dismissed, it is never shown again for any model

related to CON-2301

Checklist

• [] I've read the contributing guide
• [] The relevant docs, if any, have been updated or created
• [] The relevant tests, if any, have been updated or created

Screenshots

[ For visual changes, include screenshots. Screen recordings are particularly helpful, and appreciated! ]

https://github.com/user-attachments/assets/3501a176-3128-4457-be00-275b3e28700b

Tests

[ What tests were added or updated to ensure the changes work as expected? ]