use plugin-kit go module to register to massa station rather than hello world plugin pkg

[fleandrei]

No description provided.

[Copilot]

Pull Request Overview

This PR refactors the plugin registration mechanism to use the official plugin-kit Go module from massa station instead of the hello world plugin package. The changes modernize the plugin architecture by adopting the standard plugin-kit interface and updating Go toolchain requirements.

• Replaces hello world plugin dependency with official plugin-kit module
• Updates Go version to 1.24.6 (removing separate toolchain specification)
• Fixes string formatting in error message

Reviewed Changes

Copilot reviewed 3 out of 5 changed files in this pull request and generated no comments.

File	Description
plugin/int/api/api.go	Updates import and function call to use plugin-kit instead of hello world plugin
plugin/go.mod	Removes hello world plugin dependency and adds plugin-kit, updates Go version
plugin/int/server/manager.go	Fixes error message formatting to prevent potential issues

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