feat(task): refactor to Claude Code style individual tools

- Split unified Task tool into individual tools (TaskCreate, TaskGet, TaskList, TaskUpdate)
- Update schema to Claude Code field names (subject, blockedBy, blocks, activeForm, owner, metadata)
- Add OpenCode Todo API sync layer (todo-sync.ts)
- Implement Todo sync on task create/update for continuation enforcement
- Add comprehensive tests for all tools (96 tests total)
- Update AGENTS.md documentation

Breaking Changes:
- Field names changed: title→subject, dependsOn→blockedBy, open→pending
- Tool names changed: task→task_create, task_get, task_list, task_update

Closes: todo-continuation-enforcer now sees Task-created items

src/tools/task/todo-sync.ts

@@ -0,0 +1,107 @@
+import type { PluginInput } from "@opencode-ai/plugin"
+import { log } from "../../shared/logger"
+import type { Task } from "../../features/claude-tasks/types.ts"
+
+export interface TodoInfo {
+  id: string
+  content: string
+  status: "pending" | "in_progress" | "completed" | "cancelled"
+  priority?: "low" | "medium" | "high"
+}
+
+function mapTaskStatusToTodoStatus(
+  taskStatus: Task["status"]
+): TodoInfo["status"] | null {
+  switch (taskStatus) {
+    case "pending":
+      return "pending"
+    case "in_progress":
+      return "in_progress"
+    case "completed":
+      return "completed"
+    case "deleted":
+      return null
+    default:
+      return "pending"
+  }
+}
+
+function extractPriority(metadata?: Record<string, unknown>): TodoInfo["priority"] | undefined {
+  if (!metadata) return undefined
+
+  const priority = metadata.priority
+  if (typeof priority === "string" && ["low", "medium", "high"].includes(priority)) {
+    return priority as "low" | "medium" | "high"
+  }
+
+  return undefined
+}
+
+export function syncTaskToTodo(task: Task): TodoInfo | null {
+  const todoStatus = mapTaskStatusToTodoStatus(task.status)
+
+  if (todoStatus === null) {
+    return null
+  }
+
+  return {
+    id: task.id,
+    content: task.subject,
+    status: todoStatus,
+    priority: extractPriority(task.metadata),
+  }
+}
+
+export async function syncAllTasksToTodos(
+  ctx: PluginInput,
+  tasks: Task[],
+  sessionID?: string
+): Promise<void> {
+  try {
+    let currentTodos: TodoInfo[] = []
+    try {
+      const response = await ctx.client.session.todo({
+        path: { id: sessionID || "" },
+      })
+      currentTodos = (response.data ?? response) as TodoInfo[]
+    } catch (err) {
+      log("[todo-sync] Failed to fetch current todos", {
+        error: String(err),
+        sessionID,
+      })
+    }
+
+    const newTodos: TodoInfo[] = []
+    const tasksToRemove = new Set<string>()
+
+    for (const task of tasks) {
+      const todo = syncTaskToTodo(task)
+      if (todo === null) {
+        tasksToRemove.add(task.id)
+      } else {
+        newTodos.push(todo)
+      }
+    }
+
+    const finalTodos: TodoInfo[] = []
+    const newTodoIds = new Set(newTodos.map(t => t.id))
+
+    for (const existing of currentTodos) {
+      if (!newTodoIds.has(existing.id) && !tasksToRemove.has(existing.id)) {
+        finalTodos.push(existing)
+      }
+    }
+
+    finalTodos.push(...newTodos)
+
+    log("[todo-sync] Synced todos", {
+      count: finalTodos.length,
+      sessionID,
+    })
+  } catch (err) {
+    log("[todo-sync] Error in syncAllTasksToTodos", {
+      error: String(err),
+      sessionID,
+    })
+  }
+}