fix: correct parameter names for taskmark (taskId) and metadelete (id)

Verified via FW_DEBUG=1: taskmark expects 'taskId' (not 'metaId'),
metadelete expects 'id' (not 'metaId'). Wrong names caused silent
no-ops because the API wraps errors in a00.un.un instead of top-level
un/ex, bypassing the standard error check in fw_client.

Also documents verified response structures in SPEC.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/mcp_familywall/server.py

@@ -428,7 +428,7 @@ def toggle_task(task_id: str, complete: bool) -> str:
         JSON success indicator or an error message.
     """
     params: dict[str, Any] = {
-        "metaId": task_id,
+        "taskId": task_id,  # verified: taskmark uses 'taskId', not 'metaId'
         "complete": "true" if complete else "false",
     }
 
@@ -462,7 +462,9 @@ def delete_task(task_id: str) -> str:
         JSON success indicator or an error message.
     """
     try:
-        _authenticated_call("metadelete", {"metaId": task_id})
+        _authenticated_call(
+            "metadelete", {"id": task_id}
+        )  # verified: metadelete uses 'id', not 'metaId'
     except RuntimeError as exc:
         return f"Error: {exc}"