Fix critical architecture gaps from review

- Handler signature: PluginInput is captured at init time via closure,
  not passed to execute handlers. ToolContext is the per-invocation
  context. This matches how open-memory actually works.
- Added @alkdev/typebox as explicit direct dependency (was transitive)
- Fixed TypeBox import path: Value comes from @alkdev/typebox/value
- Clarified cost operation args: bundled into WorkflowCostOptions object
- Added Zod/TypeBox distinction note in tool definition section
- Added todowrite to relationship table
- Resolved open question about show including full body

bun.lock

@@ -6,6 +6,7 @@
       "name": "@alkdev/open-tasks",
       "dependencies": {
         "@alkdev/taskgraph": "^0.0.2",
+        "@alkdev/typebox": "^0.34.49",
         "@opencode-ai/plugin": "^1.1.3",
       },
       "devDependencies": {