REFACTOR: Promote multi-turn attack constants & defaults to ClassVar

[Roman Lutz (romanlutz)]

Continues the constants-audit cleanup established by #1964 (backend / registry / setup) and #1965 (prompt_converter). This PR combines two tracks for the multi-turn attacks so reviewers see the full picture per attack class:

• Track A: promote the module-level _ADVERSARIAL_REQUIREMENTS TargetRequirements sentinel onto the owning attack class as a ClassVar.
• Track B: lift hard-coded constructor defaults onto the owning class as DEFAULT_* ClassVars, using the sentinel-default pattern (x: int | None = None, then if x is None: x = self.DEFAULT_X) so values remain inheritable/overridable and stay self-documenting.

Files

• pyrit/executor/attack/multi_turn/crescendo.py

  • _ADVERSARIAL_REQUIREMENTS → CrescendoAttack._ADVERSARIAL_REQUIREMENTS: ClassVar[TargetRequirements]
  • max_backtracks: int = 10 → DEFAULT_MAX_BACKTRACKS: ClassVar[int] = 10
  • max_turns: int = 10 → DEFAULT_MAX_TURNS: ClassVar[int] = 10

• pyrit/executor/attack/multi_turn/red_teaming.py

  • _ADVERSARIAL_REQUIREMENTS → RedTeamingAttack._ADVERSARIAL_REQUIREMENTS: ClassVar[TargetRequirements]
  • max_turns: int = 10 → DEFAULT_MAX_TURNS: ClassVar[int] = 10

• pyrit/executor/attack/multi_turn/tree_of_attacks.py

  • _ADVERSARIAL_REQUIREMENTS → TreeOfAttacksWithPruningAttack._ADVERSARIAL_REQUIREMENTS: ClassVar[TargetRequirements]
  • tree_width: int = 3 → DEFAULT_TREE_WIDTH: ClassVar[int] = 3
  • tree_depth: int = 5 → DEFAULT_TREE_DEPTH: ClassVar[int] = 5
  • branching_factor: int = 2 → DEFAULT_BRANCHING_FACTOR: ClassVar[int] = 2
  • desired_response_prefix: str = "Sure, here is" → DEFAULT_DESIRED_RESPONSE_PREFIX: ClassVar[str] = "Sure, here is"
  • batch_size: int = 10 → DEFAULT_BATCH_SIZE: ClassVar[int] = 10

• pyrit/executor/attack/multi_turn/pair.py (Track B only — no module-level _ADVERSARIAL_REQUIREMENTS existed here)

  • tree_width: int = 3 → PAIRAttack.DEFAULT_TREE_WIDTH: ClassVar[int] = 3
  • tree_depth: int = 5 → PAIRAttack.DEFAULT_TREE_DEPTH: ClassVar[int] = 5
  • desired_response_prefix: str = "Sure, here is" → PAIRAttack.DEFAULT_DESIRED_RESPONSE_PREFIX: ClassVar[str] = "Sure, here is"
  • batch_size: int = 10 → PAIRAttack.DEFAULT_BATCH_SIZE: ClassVar[int] = 10

Docstrings updated to point at the DEFAULT_* symbols (e.g. tree_width: defaults to ``DEFAULT_TREE_WIDTH`` (3)). Public call signatures stay keyword-only with the same parameter names; only the defaults moved from inline literals to class attributes.

No value or behaviour changes

Pure structural rename. All literals preserved; same defaults applied via the sentinel pattern. Validation order is preserved (is None substitution runs before existing positive/non-negative range checks).

Verified

uv run --link-mode=copy ruff check pyrit/executor/attack/multi_turn/
uv run --link-mode=copy ty check pyrit/executor/attack/multi_turn/
uv run --link-mode=copy pytest tests/unit/executor/attack/multi_turn/ -x --no-header -q

All green — 319 passed in the multi_turn test suite, ruff/ty clean.

[Roman Lutz (romanlutz)]

Closing per maintainer feedback on the constants-audit work.

This PR mixed two concerns: (1) the A-4 portion — promoting the module-level _ADVERSARIAL_REQUIREMENTS to a class-level ClassVar on each multi-turn attack — which matches the desired pattern, and (2) the B-3 portion — promoting hyperparameter defaults (max_turns, max_backtracks, tree_width, etc.) to DEFAULT_* ClassVars via the sentinel-default pattern (int = 10 → int | None = None). The latter widens public __init__ signatures, which is not desired.

Branch romanlutz/refactor-multiturn-attack-constants left intact; the A-4 portion can be re-extracted into a clean PR if you want it merged separately. Pure A-track PRs (#1964, #1965, #1972, #1973, #1974, #1975) remain open.