Implement graceful handling of requests/rate limits

[vaivanov95]

Validations

• [x] I believe this is a way to improve. I'll try to join the Continue Discord for questions
• [x] I'm not able to find an open issue that requests the same enhancement

Problem

Currently if during response generation an HTTP 429 code is returned from e.g. Anthropic API, the generation process halts an an error is displayed.

Solution

Potential solution

• suspend the generation for a minute and then continue
  • while the generation is suspended display a message explaining the situation: "API usage limit exceeded, retrying after (counting)"
  • display a button to trigger a retry immediately