The Weapon Bond rule describes summoning as teleporting the weapon.
There is no rule (that I am aware of) indicating an appendage of a creature can be teleported separately from the creature.
The only rules regarding separating appendages from creatures is an optional rule for lingering injuries (DMG 273) which stipulates criteria which would not be met in this case.
- They take a critical hit
- They are dropped to 0 HP but aren’t killed
- They fail a death saving throw by 5 or more
Since the natural weapon “Cat claws” is summoned and they can’t be separated from the ‘cat creature’ by teleportation, then the cat is transported whole.
The cats natural weapons are an appendage of the creature, the summoning teleports the natural weapon “Claws” but these claws are integral to the cat, so the cat itself is summoned.
To bring the point home I’ll make an analogy. When an Eldridge Knight summons a sword, the hilt and pommel are also teleported, even if they are very ornate.
Can an Eldritch Knight bond with natural weapons?
This well reasoned answer indicates yes.