feat(plugin): Bundle hosted Hamster MCP across hosts

[harveyfullstack]

What changed

Installing the Hamster plugin for Claude Code, Cursor, or Codex now provisions the same hosted MCP connection. Each host prompts people to sign in to their Hamster workspace with OAuth on first use. Each skill also has a name that matches its folder, so Cursor can list it as ask, ship, and the rest instead of a cache-directory label.

Why it matters

The plugins previously installed Hamster skills and agents without consistently connecting the MCP server they depend on. People could finish installation and still have to configure that connection separately.

How it works

• One root .mcp.json declares the hosted https://tryhamster.com/mcp endpoint without bundled credentials.
• The Claude Code, Cursor, and Codex manifests all reference that shared file.
• Cursor imports the repository through Plugins, while Codex installs it through its plugin marketplace.
• The obsolete direct $CODEX_HOME/plugins installer and undocumented Codex-only marketplace catalog are removed in favor of Codex's documented marketplace flow.
• Shared skills keep their existing argument behavior and add the required name field.

Validation

• Claude Code, Cursor, and Codex load the shared Hamster MCP configuration and enter the expected authentication-required state.
• OAuth discovery, Cursor callback registration, and Codex PKCE authorization initiation succeed against the hosted endpoint.
• JSON parsing, shell syntax checking, strict Claude plugin validation, and diff checks pass.