semcode__lore_search seems to only consider lkml posts

From my agent:

```
Called tool: semcode__lore_search ✅ 0s

Tool: lore_search
Server: semcode
Arguments:
message_id: "20260520182213.872945-1-richard.henderson@linaro.org"

Output: Looking up email with message_id: 20260520182213.872945-1-richard.henderson@linaro.org

Info: Email not found with message_id: 20260520182213.872945-1-richard.henderson@linaro.org

Thought 0s
**Investigating Search Limitations**

I'm puzzled. It seems the data isn't directly indexed, as initially expected. However, I found a matching item via `b4 shazam` at `lore.kernel.org/all/20260520182213.872945-1-richard.henderson@linaro.org/t.mbox.gz`. This suggests the core issue might be an incomplete index, or perhaps some specific search constraints I haven't accounted for. I need to investigate the indexing process or search parameters.
```

the agent then falls back to using b4 to fetch the whole thread and extract the cover letter. For reference the thread can be found here: https://lore.kernel.org/all/?q=20260520182213.872945-1-richard.henderson@linaro.org