feat(max): Show taxonomy planning substeps

[Twixes]

Changes

Now you get to see what analysis steps are being taken, for a better feeling of progress and grounding:

A couple flyby improvements:

• Tuned UI rounding, as I think I went overboard earlier – let's keep the rounding larger than elsewhere in the UI, for more of a "natural" feeling of conversation, but not so massive
• Handling for rate limit errors (status 429), which I ran into
• Restored "Max is generating this answer one more time" message, which I accidentally removed previously

How did you test this code?

• Assistant tests verifying steps ✅ Added TestAssistant
• Stories ❌ Attempted, but unfortunately the version of msw we use to mock responses from our API doesn't quite work with streaming. It can't mock an in-progress stream, which is the only case where substeps appear. Open to workaround ideas

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Size Change: 0 B

Total Size: 1.16 MB

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| Filename | Size | | :--- | :---: | | `frontend/dist/toolbar.js` | 1.16 MB |

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📸 UI snapshots have been updated

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