docs: describe V2 qualified decision labels

[abrichr]

Summary

• document the V2 qualification-approved entity label contract
• describe exact qualification and bundle binding, explicit negotiation, and
  the V1 record / item fallback
• state that values from screenshots, OCR, parameters, application names, and
  models are not accepted as entity-label sources

Release dependency

This is documentation for the coordinated Types, Flow, Desktop, and Cloud V2
release. Do not merge or publish it as an available capability before the V2
producer, consumers, and negotiated capability are released together.

Validation

• git diff --check