fix(acms): correct DEFAULT_MAX_* constants in context_tier_settings and fix @when decorator in TDD step

Fix two bugs causing unit_tests CI failure:

1. context_tier_settings.py: DEFAULT_MAX_TOKENS_HOT was 8000 (should be
   16000), DEFAULT_MAX_DECISIONS_WARM was 500 (should be 100),
   DEFAULT_MAX_DECISIONS_COLD was 5000 (should be 500). These constants
   are used as getattr() fallbacks in budget_from_settings() when Settings
   attributes are missing.

2. tdd_context_tier_defaults_1443_steps.py: step "I inspect the budget
   defaults" was decorated with @then instead of @when, causing an
   UndefinedStep error since the feature file uses "When I inspect the
   budget defaults".

ISSUES CLOSED: #1443

features/steps/tdd_context_tier_defaults_1443_steps.py

@@ -42,7 +42,7 @@ def step_given_default_tier_budget(context: Any) -> None:
     context.budget = TierBudget()
 
 
-@then("I inspect the budget defaults")
+@when("I inspect the budget defaults")
 def step_then_inspect_budget_defaults(context: Any) -> None:
     assert hasattr(context, "budget")
     context._budget_hot: int = context.budget.max_tokens_hot

src/cleveragents/application/services/context_tier_settings.py

@@ -18,9 +18,9 @@ from cleveragents.domain.models.acms.tiers import TierBudget
 # Default budget when settings are not provided
 # ---------------------------------------------------------------------------
 
-DEFAULT_MAX_TOKENS_HOT = 8000
-DEFAULT_MAX_DECISIONS_WARM = 500
-DEFAULT_MAX_DECISIONS_COLD = 5000
+DEFAULT_MAX_TOKENS_HOT = 16000
+DEFAULT_MAX_DECISIONS_WARM = 100
+DEFAULT_MAX_DECISIONS_COLD = 500
 
 # ---------------------------------------------------------------------------
 # Default runtime policy values