Cap options budget-full sizing at min(balance, trade budget) with UI hint.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_options_budget_full.py

@@ -0,0 +1,16 @@
+"""按可用余额打满:min(余额, 单笔预算)."""
+from __future__ import annotations
+
+from lib.options.options_pricing_lib import resolve_budget_full_usdc
+
+
+def test_balance_above_budget_uses_budget():
+    assert resolve_budget_full_usdc(100.0, 10.0) == 10.0
+
+
+def test_balance_below_budget_uses_balance():
+    assert resolve_budget_full_usdc(5.0, 10.0) == 5.0
+
+
+def test_balance_equals_budget():
+    assert resolve_budget_full_usdc(10.0, 10.0) == 10.0