Add describe_api() method for API introspection and method discovery

[mandeepsingh2007]

Summary

Add a describe_api() method to AnophelesDataResource that lists all available public API methods with their descriptions and categories. This provides a programmatic way for users to discover and explore the API surface.

Motivation

Currently, users need to browse documentation or source code to find available methods. A built-in introspection method makes the API self-documenting and more accessible, particularly for users unfamiliar with the package.

This is also foundational for potential natural-language interfaces (ref: GSoC 2026 Project — "Exploring natural-language interfaces to increase the understanding of malaria vector genomic data"), where an NLP system would need to programmatically discover available API methods before mapping user queries to them.

Implementation

• New mixin class AnophelesDescribe in malariagen_data/anoph/describe.py
• describe_api() returns a pandas DataFrame with columns:
  • method — public method name
  • summary — first line of docstring
  • category — "data", "analysis", or "plot"
• Optional category parameter to filter results
• Follows existing cooperative mixin architecture
• 14 unit tests added in tests/anoph/test_describe.py

Example usage

import malariagen_data
ag3 = malariagen_data.Ag3()
ag3.describe_api()                     # all methods
ag3.describe_api(category="plot")      # only plotting methods
ag3.describe_api(category="data")      # only data access methods