[TSP] signature help on protocols

[kinto0]

Environment data

• Pylance trunk
• Pyrefly 0.63.1
• Type server set to Pyrefly

Code snippet + repro

Repro Steps

• type hierarchy request on Base
• type hierararchy does not work (empty response)
• notice error message (maybe unrelated?)

2026-04-29 10:44:05.963 [trace] Received response 'typeHierarchy/subtypes - (1242)' in 5ms. Request failed: Request typeHierarchy/subtypes failed with message: Cannot read properties of undefined (reading 'decoratorDataClassBehaviors') (-32603).
2026-04-29 10:44:05.963 [error] Request typeHierarchy/subtypes failed.
 Message: Request typeHierarchy/subtypes failed with message: Cannot read properties of undefined (reading 'decoratorDataClassBehaviors')
 Code: -32603