feat: initial Spaghetti UE5 Agent Plugin (Agent Plugins 1.0.0)

Agent Plugins 1.0.0 distribution package for Spaghetti Unreal AI Workbench.

Structure:
- plugin.json: manifest (spaghetti-ue5 v0.1.0, Tinirau Ltd, MIT)
- mcp.json: streamable-http → https://mcp.spaghetti.gg (OAuth, no secrets)
- skills/ue5-unreal/SKILL.md: AI-facing tool routing for Crash Investigator,
  Asset Janitor, Smart Librarian, Tool-Maker + safety defaults
- README.md: install (npx plugins add), auth (OAuth browser flow), .spaghetti
  context note
- LICENSE: MIT

OAuth flow: client connects → 401 + WWW-Authenticate → RFC 9728 metadata →
GoTrue SSO → token. All server-side; no client-side secrets.

.spaghetti context file: {team_id, project_id} at the UE project root.
The mcp_server field is not included — mcp.json owns the URL.

README.md

@@ -0,0 +1,65 @@
+# Spaghetti UE5 Agent Plugin
+
+Agent Plugins 1.0.0 distribution package for [Spaghetti Unreal AI Workbench](https://spaghetti.gg) — AI-powered tools for Unreal Engine 5.8 developers.
+
+## What this gives you
+
+Connects your AI coding assistant (Claude Code, Cursor, Codex, etc.) to the Spaghetti MCP server, providing:
+
+- **Crash Investigator** — paste a UE5 crash log, get a root-cause diagnosis + fix
+- **Asset Janitor** — audit naming conventions, find unused assets, check LODs
+- **Smart Librarian** — semantic search over UE5 engine docs + your team's knowledge base
+- **Tool-Maker** — generate safe Python scripts for UE5 editor automation
+
+## Install
+
+```bash
+# Universal installer (detects Claude Code, Cursor, Codex, VS Code, etc.)
+npx plugins add Tinirau/ue5-agent-plugin
+
+# Dry-run to inspect before installing
+npx plugins discover Tinirau/ue5-agent-plugin
+
+# Or, in Claude Code:
+/plugin marketplace add Tinirau/ue5-agent-plugin
+```
+
+## Authentication
+
+On first connect, your client opens a browser to sign in at [spaghetti.gg](https://spaghetti.gg) via OAuth (GoTrue). No API key or headers to configure — the OAuth flow is handled entirely by your client.
+
+## Project context
+
+Your UE5 project needs a `.spaghetti` file at its root:
+
+```json
+{
+  "team_id": "tm_your_team",
+  "project_id": "prj_your_project"
+}
+```
+
+Get these from your [spaghetti.gg dashboard](https://spaghetti.gg/dashboard). The file is safe to commit to Git/Perforce (no secrets). If it's missing, the first tool call guides you through creating it.
+
+## Structure
+
+```
+ue5-agent-plugin/
+├── plugin.json          # Agent Plugins 1.0.0 manifest
+├── mcp.json             # streamable-http → mcp.spaghetti.gg (OAuth, no embedded secrets)
+├── skills/
+│   └── ue5-unreal/
+│       └── SKILL.md     # AI-facing instructions: when/how to call each tool
+├── LICENSE
+└── README.md
+```
+
+## Requirements
+
+- An AI client that supports [Agent Plugins 1.0.0](https://agent-plugins.org) (Claude Code, Cursor, OpenAI Codex, etc.)
+- A Spaghetti account ([sign up](https://spaghetti.gg/signup))
+- UE 5.8+ (for built-in MCP tool integration; the Spaghetti tools work with 5.6+ for non-MCP features)
+
+## License
+
+MIT © Tinirau Ltd