[Julio César Suástegui (juliosuas)]

Description

Claimed and assigned as item P311-01 in #3166. This is the focused AdversarialPrompts.from_metadata follow-up and mirrors #3626 (WebSearchConfig.from_metadata).

• AdversarialPrompts.from_metadata now returns Self | None instead of AdversarialPrompts | None, so subclasses get their own type back.
• Runtime behavior is unchanged: absent associations still return None, inputs are read-only Mappings and are not mutated, and validation is unchanged.

Tests and Documentation

Added TestAdversarialPromptsFromMetadata in tests/unit/models/test_adversarial_prompts.py:

• absent association (None, {}, unrelated keys) returns None for the base class and a subclass
• present association returns the calling class (assert_type plus runtime type(...) is checks)
• JSON metadata round trip, read-only MappingProxyType input, no mutation
• invalid payloads raise ValidationError

Ran locally:

• pytest -n 4 --dist=loadfile tests/unit: 32991 passed, 32 skipped
• ty check pyrit tests/unit (make ty): all checks passed
• pre-commit run --all-files: passed

No documentation changes needed; JupyText not applicable.