add github copilot plugin

[itsdouges]

Adds a GitHub Copilot plugin using the new stdio mcp cli.

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Note

Low Risk
Changes are limited to plugin metadata, JSON schemas, CI validation, and documentation—no application runtime or security-sensitive logic.

Overview
Adds GitHub Copilot / VS Code agent plugin packaging so paper-desktop can be installed from the paper-design/agent-plugins marketplace, with a stdio MCP entry pointing at ~/.paper/bin/paper mcp.

Introduces an Agent Plugins 1.0.0 manifest for paper-desktop (plugin.json + updated mcp.json with $schema and explicit type: "stdio"), a Copilot marketplace at .github/plugin/marketplace.json, and AJV schemas plus validate-copilot.mjs hooked into build/test. README documents Copilot CLI install, VS Code marketplace settings, and optional manual MCP config.

Claude and Cursor marketplace JSON drops the metadata.version field to align with the new layout.

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[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

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[cursor]

Marketplace source rejects valid paths

Medium Severity

isValidRelativePath requires a ./ prefix on marketplace source (and mcpServers file paths), but GitHub Copilot’s marketplace docs treat that prefix as optional and accept entries like plugins/paper-desktop. Those spec-valid manifests fail CI even though the CLI would resolve them correctly.

 

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