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.

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Tinirau Ltd
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.