Description

When expanding a task into subtasks using task-master expand, each subtask is assigned dependencies referencing only the subtask's numeric ID (e.g., 2, 3, etc.). However, these dependencies are not treated as fully-qualified IDs (like 16.2), which leads to broken references and validation errors. Additionally, these dependencies are not visible in the task-master show command, making the issue harder to notice.

Furthermore, if a subtask is promoted to a full task via task-master move, its dependency is preserved as-is (e.g., 8) rather than updated to reflect its new context, further compounding the issue.

Steps to Reproduce

1. Start with a clean state and create a new task.

2. Run task-master expand --id=16 --num=0 to expand the task into subtasks.

3. Observe that the generated subtasks have sequential numeric IDs and dependencies:

   "subtasks": [
     { "id": 1, "dependencies": [] },
     { "id": 2, "dependencies": [1] },
     { "id": 3, "dependencies": [2] },
     ...
     { "id": 9, "dependencies": [8] }
   ]

4. Promote the last subtask to a new task:

   task-master move --id=16.9 --to=21

5. Run validation:

   task-master validate-dependencies

6. Observe that dependency errors are reported:

   [ERROR] Dependency validation failed. Found 8 issue(s):
   [ERROR]   [MISSING] Task 16.2: Subtask 16.2 depends on non-existent task/subtask 1 (Dependency: 1)
   [ERROR]   [MISSING] Task 16.3: Subtask 16.3 depends on non-existent task/subtask 2 (Dependency: 2)
   [ERROR]   [MISSING] Task 16.4: Subtask 16.4 depends on non-existent task/subtask 3 (Dependency: 3)
   [ERROR]   [MISSING] Task 16.5: Subtask 16.5 depends on non-existent task/subtask 4 (Dependency: 4)
   [ERROR]   [MISSING] Task 16.6: Subtask 16.6 depends on non-existent task/subtask 5 (Dependency: 5)
   [ERROR]   [MISSING] Task 16.7: Subtask 16.7 depends on non-existent task/subtask 6 (Dependency: 6)
   [ERROR]   [MISSING] Task 16.8: Subtask 16.8 depends on non-existent task/subtask 7 (Dependency: 7)
   [ERROR]   [MISSING] Task 21: Task 21 depends on non-existent task 8 (Dependency: 8)
   

Expected Behavior

• Dependencies within subtasks should be stored using fully-qualified IDs in the form of <parent_id>.<subtask_id> (e.g., 16.2, 16.3, etc.).
• task-master validate-dependencies should not fail due to invalid subtask references.
• When promoting a subtask to a standalone task, its dependencies should be rewritten appropriately or dropped if invalid.
• The task-master show command should optionally display subtask dependencies to reveal these issues in the UI.

Actual Behavior

• Subtask dependencies are stored as numeric-only IDs (e.g., 2, 3, etc.), causing them to be interpreted as global task IDs.
• These invalid references are not visible via task-master show, making them difficult to detect.
• Promoted subtasks retain references to nonexistent task IDs.
• task-master validate-dependencies fails due to missing dependencies.
• task-master fix-dependencies does not fix these invalid subtask dependency references.

Screenshots or Logs

Please see above

Environment

• Task Master version: v0.20.0
• Node.js version: v24.3.0
• Operating system: Windows 11
• IDE (if applicable): VSCode