feat: add claude code plugin support (#1293)

Co-authored-by: Claude <noreply@anthropic.com>

packages/claude-code-plugin/commands/convert-task-to-subtask.md

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+Convert an existing task into a subtask.
+
+Arguments: $ARGUMENTS
+
+Parse parent ID and task ID to convert.
+
+## Task Conversion
+
+Converts an existing standalone task into a subtask of another task.
+
+## Argument Parsing
+
+- "move task 8 under 5"
+- "make 8 a subtask of 5"
+- "nest 8 in 5"
+- "5 8" → make task 8 a subtask of task 5
+
+## Execution
+
+```bash
+task-master add-subtask --parent=<parent-id> --task-id=<task-to-convert>
+```
+
+## Pre-Conversion Checks
+
+1. **Validation**
+   - Both tasks exist and are valid
+   - No circular parent relationships
+   - Task isn't already a subtask
+   - Logical hierarchy makes sense
+
+2. **Impact Analysis**
+   - Dependencies that will be affected
+   - Tasks that depend on converting task
+   - Priority alignment needed
+   - Status compatibility
+
+## Conversion Process
+
+1. Change task ID from "8" to "5.1" (next available)
+2. Update all dependency references
+3. Inherit parent's context where appropriate
+4. Adjust priorities if needed
+5. Update time estimates
+
+## Smart Features
+
+- Preserve task history
+- Maintain dependencies
+- Update all references
+- Create conversion log
+
+## Example
+
+```
+/taskmaster:add-subtask/from-task 5 8
+→ Converting: Task #8 becomes subtask #5.1
+→ Updated: 3 dependency references
+→ Parent task #5 now has 1 subtask
+→ Note: Subtask inherits parent's priority
+
+Before: #8 "Implement validation" (standalone)
+After:  #5.1 "Implement validation" (subtask of #5)
+```
+
+## Post-Conversion
+
+- Show new task hierarchy
+- List updated dependencies
+- Verify project integrity
+- Suggest related conversions