docs : add create-group and update-group tools to MCP spec

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/superpowers/specs/2026-03-15-mcp-server-design.md

@@ -41,7 +41,9 @@ src/Mcp/
 │   │   ├── ListPrioritiesTool.php
 │   │   ├── ListEffortsTool.php
 │   │   ├── ListTagsTool.php
-│   │   └── ListGroupsTool.php
+│   │   ├── ListGroupsTool.php
+│   │   ├── CreateGroupTool.php
+│   │   └── UpdateGroupTool.php
 │   ├── TimeEntry/
 │   │   ├── ListTimeEntriesTool.php
 │   │   ├── CreateTimeEntryTool.php
@@ -247,9 +249,9 @@ location /_mcp {
 - **Returns**: `{ success: true, message: "Task PROJECT-123 deleted" }`
 - **Implementation**: `EntityManager::remove()` + flush (cascade deletes documents)
 
-### TaskMeta Tools (Read-Only)
+### TaskMeta Tools
 
-Statuses, priorities, efforts, and tags are **global** (shared across all projects). Groups are **per-project**.
+Statuses, priorities, efforts, and tags are **global** (shared across all projects, read-only via MCP). Groups are **per-project** (read/create/update).
 
 #### `list-statuses`
 - **Description**: List all task statuses (needed to create/update tasks)
@@ -277,6 +279,27 @@ Statuses, priorities, efforts, and tags are **global** (shared across all projec
 - **Returns**: Array of `{ id, title, description, color, project: { id, code, name }, archived }`
 - **Implementation**: `TaskGroupRepository` with optional project filter
 
+#### `create-group`
+- **Description**: Create a new task group for a project
+- **Parameters**:
+  - `projectId` (int, required)
+  - `title` (string, required)
+  - `description` (string, optional)
+  - `color` (string, optional, default: #222783)
+- **Returns**: Created group object
+- **Implementation**: Create `TaskGroup` entity, set project relation, persist
+
+#### `update-group`
+- **Description**: Update an existing task group (partial update)
+- **Parameters**:
+  - `id` (int, required)
+  - `title` (string, optional)
+  - `description` (string, optional)
+  - `color` (string, optional)
+  - `archived` (bool, optional)
+- **Returns**: Updated group object
+- **Implementation**: Find group, apply changes, flush
+
 ### TimeEntry Tools
 
 #### `list-time-entries`