Expose Subtasks as first class resources in the MCP API

It would be great if Subtasks were exposed as first class entities for both Aki and MCP compatible assistants, with the same level of support that Tasks currently have.

Right now, assistants such as Aki, ChatGPT, Codex, Claude, and other MCP compatible clients can perform the following operations on Tasks:

• Read

• Create

• Update

• Delete

• Complete

• Plan and reschedule

• Reorganize

The current limitation is that Subtasks are not exposed as actionable entities for Aki or other MCP compatible clients. As a consequence, when asking an assistant to create a task with several subtasks, it typically falls back to writing a checklist inside the task description instead of creating actual Subtasks.

Ideally, both Aki and the MCP integration should support operations such as:

• Read subtasks

• Create subtasks

• Update subtasks

• Delete subtasks

• Complete/uncomplete subtasks

• Reorder subtasks

• Move subtasks between parent tasks

• Convert a task into a subtask, and vice versa if supported

This would allow AI assistants to treat Subtasks as first class entities and interact with them in the same way they currently interact with Tasks.