Package and release Git-Ape as a VS Code extension (VSIX)

[arnaudlh]

Summary

Add CI/CD workflows and extension scaffolding to package Git-Ape as a distributable VS Code extension (VSIX) and publish it via GitHub Releases.

Motivation

Currently Git-Ape can only be consumed by cloning the repository. Packaging it as a VSIX extension allows users to install it directly in VS Code, making the agents, skills, and instructions discoverable through the Copilot Chat extension marketplace.

Scope

GitHub Actions Workflows

• Build workflow — triggered on PRs that touch agents, skills, instructions, plugin config, or extension files. Packages the VSIX as a build artifact for validation.
• Release workflow — triggered on version tags (v*). Packages the VSIX and publishes it as a GitHub Release with auto-generated release notes.
• Both workflows assemble the extension payload by copying LICENSE and .github/ into the extension/ directory before packaging.

Extension Scaffolding

• VS Code extension manifest — declares all chat agents and chat skills. Publisher: azure, category: Chat.
• Plugin metadata — name, description, version, author, keywords, agent/skill directory pointers.
• Extension icon

.gitignore Updates

• Ignore extension build artifacts (extension/package.json, extension/*.vsix, extension/.github/, extension/LICENSE, node_modules/)
• Ignore Docusaurus build output (docs/docusaurus/)

Implementation Notes

• The extension is purely declarative (markdown agents/skills) — no bundling or compilation step needed.
• package.template.json is used as the source of truth; it gets copied to package.json at build time (the generated package.json is gitignored).
• Repository URLs should point to Azure/git-ape.

Acceptance Criteria

• PR builds produce a downloadable VSIX artifact
• Pushing a v* tag creates a GitHub Release with the VSIX attached
• The packaged VSIX installs in VS Code and registers all agents and skills in Copilot Chat
• Extension build artifacts are properly gitignored

References

• Prior implementation: Azure/git-ape-private#37