docs: add Task system documentation

- Document TaskCreate, TaskGet, TaskList, TaskUpdate tools
- Note that these tools follow Claude Code internal specs but are not officially documented by Anthropic
- Include schema, dependency system, and usage examples

docs/task-system.md

@@ -0,0 +1,94 @@
+# Task System
+
+Oh My OpenCode's Task system provides structured task management with dependency tracking and parallel execution optimization.
+
+## Note on Claude Code Alignment
+
+This implementation follows Claude Code's internal Task tool signatures (`TaskCreate`, `TaskUpdate`, `TaskList`, `TaskGet`) and field naming conventions (`subject`, `blockedBy`, `blocks`, etc.).
+
+**However, Anthropic has not published official documentation for these tools.** The Task tools exist in Claude Code but are not documented on `docs.anthropic.com` or `code.claude.com`.
+
+This is **Oh My OpenCode's own implementation** based on observed Claude Code behavior and internal specifications.
+
+## Tools
+
+| Tool | Purpose |
+|------|---------|
+| `TaskCreate` | Create a task with auto-generated ID (`T-{uuid}`) |
+| `TaskGet` | Retrieve full task details by ID |
+| `TaskList` | List active tasks with unresolved blockers |
+| `TaskUpdate` | Update status, dependencies, or metadata |
+
+## Task Schema
+
+```ts
+interface Task {
+  id: string              // T-{uuid}
+  subject: string         // Imperative: "Run tests"
+  description: string
+  status: "pending" | "in_progress" | "completed" | "deleted"
+  activeForm?: string     // Present continuous: "Running tests"
+  blocks: string[]        // Tasks this blocks
+  blockedBy: string[]     // Tasks blocking this
+  owner?: string          // Agent name
+  metadata?: Record<string, unknown>
+  threadID: string        // Session ID (auto-set)
+}
+```
+
+## Dependencies and Parallel Execution
+
+```
+[Build Frontend]    ──┐
+                      ├──→ [Integration Tests] ──→ [Deploy]
+[Build Backend]     ──┘
+```
+
+- Tasks with empty `blockedBy` run in parallel
+- Dependent tasks wait until blockers complete
+
+## Example Workflow
+
+```ts
+TaskCreate({ subject: "Build frontend" })                    // T-001
+TaskCreate({ subject: "Build backend" })                     // T-002
+TaskCreate({ subject: "Run integration tests",
+             blockedBy: ["T-001", "T-002"] })                 // T-003
+```
+
+```ts
+TaskList()
+// T-001 [pending] Build frontend        blockedBy: []
+// T-002 [pending] Build backend         blockedBy: []
+// T-003 [pending] Integration tests     blockedBy: [T-001, T-002]
+```
+
+```ts
+TaskUpdate({ id: "T-001", status: "completed" })
+TaskUpdate({ id: "T-002", status: "completed" })
+// T-003 now unblocked
+```
+
+## Storage
+
+Tasks are stored as JSON files:
+
+```
+.sisyphus/tasks/
+```
+
+## Difference from TodoWrite
+
+| Feature | TodoWrite | Task System |
+|---------|-----------|-------------|
+| Storage | Session memory | File system |
+| Persistence | Lost on close | Survives restart |
+| Dependencies | None | Full support (`blockedBy`) |
+| Parallel execution | Manual | Automatic optimization |
+
+## When to Use
+
+Use Tasks when:
+- Work has multiple steps with dependencies
+- Multiple subagents will collaborate
+- Progress should persist across sessions