test: drive advisory tests through public record() APIs

Address CodeRabbit: the Python advisory tests set private cost fields directly,
so they'd pass even if record()/record_tool() stopped feeding advisory(). Drive
state through the public API with a deterministic manual price instead.

Author: hatimanees

tests/test_advisory.py

@@ -3,7 +3,7 @@
 
 import pytest
 
-from floe_guard import BudgetAdvisory, BudgetGuard
+from floe_guard import BudgetAdvisory, BudgetGuard, ManualPrice
 
 
 def test_fresh_guard_is_far_from_limit() -> None:
@@ -66,20 +66,21 @@ def test_expected_cost_unknown_before_first_call() -> None:
 
 def test_est_calls_remaining_after_a_call() -> None:
     g = BudgetGuard(limit_usd=1.00)
-    g._last_llm_cost = 0.10   # warm estimate; remaining is 1.00
+    # Drive state through the public API (manual price for determinism), not by
+    # poking private fields: this also proves record() feeds advisory().
+    g.record("m", 1_000, 0, price=ManualPrice(1e-4, 0.0))  # $0.10 spent, $0.90 left
     a = g.advisory()
     assert a.expected_cost == pytest.approx(0.10)
-    assert a.est_calls_remaining == 10  # floor(1.00 / 0.10)
+    assert a.est_calls_remaining == 9  # floor(0.90 / 0.10)
 
 
 def test_est_calls_remaining_uses_costlier_of_llm_and_tool() -> None:
     g = BudgetGuard(limit_usd=1.00)
-    g._last_llm_cost = 0.05
-    g._last_tool_cost = 0.20   # costlier side wins (conservative)
-    g.spent_usd = 0.40         # remaining 0.60
-    a = g.advisory()
-    assert a.expected_cost == pytest.approx(0.20)
-    assert a.est_calls_remaining == 3  # floor(0.60 / 0.20)
+    g.record("m", 1_000, 0, price=ManualPrice(2e-4, 0.0))  # $0.20 LLM (costlier)
+    g.record_tool("db.query", 0.05)                        # $0.05 tool (cheaper)
+    a = g.advisory()                                       # spent 0.25, remaining 0.75
+    assert a.expected_cost == pytest.approx(0.20)          # max(llm, tool) wins
+    assert a.est_calls_remaining == 3  # floor(0.75 / 0.20)
 
 
 def test_invalid_near_limit_bps_rejected() -> None: