Add WarpGrep (Morph's RL-trained codebase search agent) as an
alternative backend for the codebase_search tool. Users bring their
own API key and WarpGrep runs in its own context window, performing
multi-turn ripgrep and file reads to find relevant code spans.
- Add warpGrepEnabled to codebaseIndexConfigSchema
- Add warpGrepApiKey to SECRET_STATE_KEYS
- Gate codebase_search on either WarpGrep or CodeIndexManager
- Try WarpGrep first in CodebaseSearchTool, fall back to vector search
- Add settings UI with toggle and API key field in CodeIndexPopover
- Persist settings via webviewMessageHandler
Closes: #11865
