High/Low level voltage specs for an IC
(edit: misunderstood a sentence in the question; I thought that you had connected Vref to the Vdd pin. I added a picture of the pinout to the question.)

Yes, it's confusing when it means that the maximum is minimum xxx :-)


  "As long as the voltage is below 0.3Vdd, the MCP3202 will regard it as a digital zero"


That's the right interpretation. 

But it's not a good idea to use the same voltage for power and ADC reference. Your power supply voltage isn't clean enough. Power should be a bit higher (what's wrong with 5 V?), and you use a voltage reference for the ADC reference voltage (maybe that's what the 4.096 V is?), or you use an RC filter to derive the reference from the 5 V if the absolute accuracy isn't important.  

The problem is not in the maximum low, and minimum high levels, but in the maximum high. The PIC will output 5 V, which is a volt higher than the ADC's supply. Absolute maximum ratings, on page 2 of the datasheet say that no voltage should exceed Vcc by more than 0.6 V. Absolute Maximum Ratings. Read below the table:  


  *Notice: Stresses above those listed under “Maximum Ratings” may
  cause permanent damage to the device. This is a stress rating only
  and functional operation of the device at those or any other conditions
  above those indicated in the operational listings of this specification is
  not implied. Exposure to maximum rating conditions for extended
  periods may affect device reliability.


(my emphasis)

So, if you would use for instance the MCP1541 as a reference you can use a 5 V supply for that, and the ADC.