Add T-shaped options chain view with straddle metrics (phase A).

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

tests/test_options_pricing.py

@@ -75,6 +75,23 @@ def test_equivalent_contract_leverage():
     assert lev == 144.9
 
 
+def test_straddle_pricing():
+    from lib.options.options_pricing_lib import (
+        format_straddle_band,
+        straddle_ask_per_unit,
+        straddle_breakeven_band,
+        straddle_premium_total,
+    )
+
+    assert straddle_ask_per_unit(0.148, 16.2) == 16.348
+    assert straddle_premium_total(0.148, 16.2, 1.0) == 16.35
+    lo, hi = straddle_breakeven_band(1800, 16.348)
+    assert lo == 1783.65
+    assert hi == 1816.35
+    assert format_straddle_band(1800, 16.348) == "1784 ~ 1816"
+    assert straddle_ask_per_unit(0.148, None) is None
+
+
 def test_estimate_expiry_value_and_profit_at_index():
     from lib.options.options_pricing_lib import (
         estimate_expiry_profit_at_index,