Add 'instant' to SearchType for lowest latency search

[devin-ai-integration]

Summary

Adds "instant" as a new search type option to the Python SDK. Instant search provides the lowest latency, optimized for real-time applications like autocomplete and live suggestions.

Changes:

• Added "instant" to the SearchType Literal type
• Updated SearchType docstring with instant description
• Updated search method docstrings to include instant in the type parameter options

Review & Testing Checklist for Human

• Verify backend support: Confirm the Exa API actually accepts type: "instant" and returns results. This SDK change assumes backend support exists.
• Test with real API call: Run a simple search with type="instant" to verify it works end-to-end

Recommended test:

from exa_py import Exa
exa = Exa()
results = exa.search("test query", type="instant", num_results=5)
print(results)

Notes

• Related docs PR: https://github.com/exa-labs/docs/pull/150
• Related exa-js PR will be created separately
• Requested by: Yi Yang
• Devin session: https://app.devin.ai/sessions/07d4f4bd22314ae6b62875385cd295a2

[devin-ai-integration]

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