Show context window and API usage quota in TUI

[MiniCodeMonkey]

Problem

Users have no visibility into context window usage or API quota limits from within Chief's TUI. They only find out about quota limits when Claude crashes with a rate limit error:

```
🔄 Claude crashed, retrying (1/3)...

You've hit your limit · resets 11pm (UTC)
```

Suggested solution

Add progress bars to the primary status screen showing:

• Context window usage — how much of the current context is consumed
• API quota usage — how close to the plan's rate limit

Claude Code exposes this information in its own UI, so there should be an API surface to read from.