Fix options mark price float junk and target index input rollback.

Skip full card redraw while the monitor target field is focused, and format mark/avg without relying on dusty server strings.

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

tests/test_options_pricing.py

@@ -21,6 +21,8 @@ def test_round_option_px():
     assert format_option_px(1370, "5") == "1370"
     assert format_option_px(1160, 5) == "1160"
     assert format_option_px(1000, "5") == "1000"
+    # 无 tick 时不得透出浮点毛刺
+    assert format_option_px(482.4881990066513, None) == "482.4882"
 
 
 def test_premium_per_sheet():