feat(example): add Anchor framework SP1 proof verifier example

[marcelofeitoza]

Summary

Adds a new example demonstrating how to use the sp1-solana verifier library within an Anchor framework-based Solana program. This example provides an alternative implementation to the existing native Solana program examples, showcasing integration with the popular Anchor development framework.

What's Changed

• New Anchor-based example: Added complete Anchor project structure under example/anchor/
• SP1 proof verification: Implements the same Fibonacci proof verification logic as existing examples but using Anchor's declarative syntax
• Test suite: Includes comprehensive TypeScript tests for the Anchor program
• Project configuration: Added proper Anchor.toml, package.json, and workspace configuration

Key Features

• Framework compatibility: Demonstrates sp1-solana works seamlessly with Anchor programs
• Consistent verification logic: Verifies SP1 Groth16 proofs for the Fibonacci sequence using the same verification key hash as other examples
• Public input parsing: Extracts and logs the first three public inputs (n, a, b) as little-endian u32 values
• Error handling: Proper validation of instruction data length (320 bytes) and proof verification results
• Testing: Complete test coverage including edge cases and error scenarios

Technical Details

• Uses Anchor v0.31.1 framework
• Maintains compatibility with existing sp1-solana verifier library
• Implements the same 320-byte instruction data format (256 bytes proof + 64 bytes public inputs)
• Uses SP1 v5.0.0 verification key bytes (GROTH16_VK_5_0_0_BYTES)

Testing

The example includes comprehensive tests covering:

• Instruction data parsing and structure validation
• Invalid data handling and error cases
• Valid proof structure processing
• Verification key hash constant validation

This addition makes the sp1-solana library more accessible to developers already familiar with the Anchor framework while maintaining full compatibility with the core verification functionality.