Whatever spell or wand will be used, with spell noise it will certainly wake up the dragon considering the distance between the mummy and the monster.
A dragon having a good MR is not good news in regard to the chance of effect of whatever is thrown at it, so using a spell would mean counting a lot on luck, and luck is usually failing in crawl when you really need it.
A polymorph other, even if by chance it works against the dragon MR would probably just give another dragon, and even if by luck it's an ice dragon, being at close quarter it would just use his claws and teeths that do not care about the cold resistance.
Walking is out of question as the character has no stealthy mention on the dump text, so it will wake up the beast that will be at 1 range and then will use the fire breath.
reading the teleportation scroll or self use of the teleport wand would take too much time to make effect, the dragon would tear the character apart in no time.
The scroll of fear would be great to buy time for another teleportation, but again it is said that MR can save, and dragons don't have small MR.
The scroll of summoning, resulting an abomination, could lead the dragon to have a chance to target the abomination for its 1st attack, but is the current crawl system always targetting the player first ?
And even if Crawl do not have the monsters always targetting the player first, if the summon does not appear next to the dragon, the player is lost to the claws and teeths.
So again, luck involved.
Personnally, i would try the scroll of fear, of course if it does not work the dragon will wake up and the character is dead in the following turn.
But other possibilities seems to involve even more luck.
Crawl has been a huge sadist in where the teleportation sent that mummy character.