Implement provider-github plugin

[mwaldheim]

Goal

Implement gRPC server for provider-github plugin following ADR-001 and plugin template.

Type

Provider

Description

Expose GitHub repository, release, tag, and metadata operations over the SemRel plugin gRPC contract. It should wrap authenticated GitHub API access and normalize responses for the core engine.

Acceptance Criteria

• gRPC server stub implemented (cmd/plugin/main.go)
• Plugin-specific logic in internal/plugin/
• Unit tests with 80%+ coverage
• Makefile build/test/lint targets working
• CI workflow passes (lint, test, build)
• README with usage examples
• Configuration documentation

Links

• Plugin Template: https://github.com/SemRels/plugin-template
• ADR-001: https://github.com/SemRels/semrel/blob/main/docs/adr/001-plugin-architecture.md
• Registry Schema: https://github.com/SemRels/semrel-registry/blob/main/schemas/plugin-metadata.json
• Related semrel issues:
• Plugin category: Provider - abstract VCS operations (github, gitlab, gitea, git) semrel#91
• Built-in plugin: GitHub Releases publisher semrel#12