House dragon stuff
I've discovered where the scratch attack is going wrong besides the other flaw already pointed out. You're trying to have them scratch with their fingers, but since you gave them the default quadruped body, they have no [GRASP] body parts, so the game cannot attach the 4FINGERS in their body, and thus they have no fingers. Fingers need grasping body parts (hands) to attach to. Checking the error log when genning a world with your dragons will give you this information, so make sure to turn on your error log.
I'm working on it right now, as I'm not quite sure what happens when you mix grasp and stance, since I assume you don't want your dragons walking on their back legs. Let me see what happens!
This, by the way, is my fix:
Add the [GRASP] tag after the [STANCE] tag in body_default.txt in the BODY:QUADRUPED entry, in the two lines for the two front feet. Copy and past the quadruped entry and rename it QUADRUPED_DRAGON or something to edit if you don't want to modify ALL quadrupeds.
Rename your dragon's body to QUADRUPED_DRAGON in the creature entry if you do this.
This should be your scratch attack:
[ATTACK:SCRATCH:CHILD_TISSUE_LAYER_GROUP:BY_TYPE:GRASP:BY_CATEGORY:FINGER]
[ATTACK_SKILL:GRASP_STRIKE]
[ATTACK_VERB:scratch:scratches]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PENETRATION_PERC:100]
[ATTACK_FLAG_EDGE]
[ATTACK_PRIORITY:SECOND]
This post prone to editing as I test. Fuguring out body tags is fun!
Testing: Biting is the preferred attack type, and so I haven't had any scratching dragons yet, BUT I'm no longer getting worldgen errors about their fingers.
Creating a new body gloss is seemingly not recognized. No idea what's wrong. I was trying to bodygloss their fingers into being called claws, since the claw_foot and claw_hand bodygloss tags are not what would be appropriate. But it's now spamming my worldgen with "unrecognized creature caste bodygloss token".