feat: add float/double encoding support and Google protobuf types

[allenday]

feat: add float/double encoding support and Google protobuf types

Summary

• Add native float/double encoding/decoding functions to ProtoBufRuntime
• Include Google well-known types runtime libraries
• Enable proper handling of validation constraints from buf/validate

Changes

Float/Double Support

• Added _decode_float() and _encode_float() functions for 32-bit float support
• Added _decode_double() and _encode_double() functions for 64-bit double support
• Enables proper handling of floating-point validation constraints

Google Well-Known Types

• GoogleProtobufDuration.sol - Support for google.protobuf.Duration messages
• GoogleProtobufTimestamp.sol - Support for google.protobuf.Timestamp messages
• GoogleProtobufFieldDescriptorProto.sol - Support for google.protobuf.FieldDescriptorProto messages
• GoogleProtobufAny.sol - Existing support documented

Technical Details

Files Modified:

• protobuf-solidity/src/protoc/plugin/runtime/ProtoBufRuntime.sol - Added float/double encode/decode functions
• README.md - Added Runtime Enhancements documentation section

Files Added:

• protobuf-solidity/src/protoc/plugin/runtime/GoogleProtobufDuration.sol
• protobuf-solidity/src/protoc/plugin/runtime/GoogleProtobufTimestamp.sol
• protobuf-solidity/src/protoc/plugin/runtime/GoogleProtobufFieldDescriptorProto.sol

New Functions:

• _decode_float(uint256 p, bytes memory bs) -> (bytes4, uint256)
• _encode_float(bytes4 x, uint256 p, bytes memory bs) -> uint256
• _decode_double(uint256 p, bytes memory bs) -> (bytes8, uint256)
• _encode_double(bytes8 x, uint256 p, bytes memory bs) -> uint256

Use Cases

This enhancement enables:

• Protobuf schemas with float/double fields to compile successfully
• buf/validate constraints on floating-point fields
• Integration with Google well-known types in Solidity contracts
• Full protobuf type coverage in generated Solidity code

Test Plan

• Verify float/double functions compile and work correctly
• Test integration with buf/validate floating-point constraints
• Confirm Google protobuf types generate proper runtime imports
• Validate backward compatibility with existing integer-only schemas

Impact

Expands the plugin's protobuf type support to include all standard types, enabling more comprehensive protobuf schema usage in Solidity projects.