Set up project scaffold: Bun/OpenCode plugin with registry pattern

- AGENTS.md adapted from taskgraph for this Bun/TypeScript plugin
- Dual MIT/Apache-2.0 licenses
- Package.json, tsconfig, biome config following open-memory pattern
- Skeleton src/ with registry-pattern tasks tool (help operation working)
- Opencode.json plugin config
- .gitignore for dist, node_modules, lockb
- Remove typo .gitingore files, proper .gitignore in .opencode/

opencode.json

@@ -0,0 +1,4 @@
+{
+  "plugin": ["@alkdev/open-tasks"],
+  "$schema": "https://opencode.ai/config.json"
+}