ChatGPT plugin, step 1: make the MCP server plugin-ready (securitySchemes, profile tool, structuredContent, manifest)

Summary Make the existing MCP server at /mcp conform to what ChatGPT requires of a published plugin, with no UI yet. After this work Outline can be submitted to the ChatGPT/Codex plugin directory as a tools-plus-skills plugin, in the same shape as the published Notion plugin. Context: OpenAI "Plugin Extensions" (DevDay, Sep 2026) turned ChatGPT apps into MCP servers plus optional UI. Outline already has the hard parts: Streamable HTTP MCP, OAuth 2.1 + PKCE, DCR, and RFC 9728 discovery. This issue covers the remaining metadata and manifest work. Follow-ups: UI cards are tracked in a separate issue; the single public MCP URL for cloud is tracked in a separate issue. Reference docs • Authentication requirements and the profile tool: • MCP server guidance: • Plugin manifest and packaging: • Plugin guidelines and review: • Example published plugin (manifests + skills): Current state • MCP route: server/routes/mcp/index.ts. createMcp…