rename Discriminant to Algorithm

[MichaelMure]

No description provided.

[Copilot]

Pull Request Overview

This PR renames the term "Discriminator" to "Algorithm" throughout the codebase to improve API clarity and naming consistency. The change affects method names, type definitions, constants, error messages, and documentation.

• Renames Discriminator type to Algorithm and updates all related constants
• Updates Discriminator() method to Algorithm() in the Varsig interface and implementations
• Changes error variable from ErrUnknownDiscriminator to ErrUnknownAlgorithm

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
varsig.go	Updates core interface method and struct field names
constant.go	Renames type definition and updates documentation
error.go	Renames error variable and message
registry.go	Updates Registry type definition and internal method names
rsa.go	Renames RSA algorithm constant and updates constructor
eddsa.go	Renames EdDSA algorithm constant and updates constructor
ecdsa.go	Renames ECDSA algorithm constant and updates constructor
varsig_test.go	Updates test assertions and expected output
registry_test.go	Updates test constants and helper functions
rsa_test.go	Updates test assertions
eddsa_test.go	Updates test assertions
common_test.go	Updates test assertions
README.md	Updates documentation example