feat(dasha): Yogini 小运按比例单列，大运输出不变

完整解读仍只看大运。小运从该大运自己的 Yogini 起按年数比例排，出生前的段丢掉。

Co-Authored-By: Grok (agent loop)
Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/yogini_dasha.py

@@ -61,10 +61,63 @@ def calculate_yogini_dasha(birth_info: dict) -> dict:
         moon_longitude: sidereal degrees, required
         as_of / today: observation instant; report callers should pass it
         dasha_year_days: fixed-day year, default 365.25
+
+    Major rows stay free of sub-periods. Callers that need antardashas use
+    ``yogini_antardashas`` on a copy.
     """
     return _calculate_moon_balanced_yogini(birth_info)
 
 
+def _as_datetime(value):
+    if isinstance(value, datetime):
+        return value
+    return datetime.fromisoformat(str(value))
+
+
+def yogini_antardashas(major_row: dict, *, birth_dt, year_days: float) -> list:
+    """Proportional antardashas inside one Yogini mahadasha.
+
+    Eight sub-periods start at this mahadasha's own Yogini and follow Goel
+    Table I. Each length is ``full_years * sub_years / 36``. They are laid out
+    from ``unclipped_start_date``. Sub-periods that end at or before birth are
+    dropped. The one that crosses birth keeps ``unclipped_start_date`` and
+    starts at birth. The last sub-period ends on the mahadasha ``end_date``.
+    """
+    birth = _as_datetime(birth_dt)
+    year_length = float(year_days)
+    if year_length <= 0:
+        raise ValueError('dasha_year_days must be positive')
+    start_idx = next(
+        index for index, item in enumerate(YOGINI_SEQUENCE) if item['name'] == major_row['yogini']
+    )
+    full_years = float(major_row['full_years'])
+    cursor = _as_datetime(major_row['unclipped_start_date'])
+    major_end = _as_datetime(major_row['end_date'])
+    rows = []
+    for offset in range(len(YOGINI_SEQUENCE)):
+        item = YOGINI_SEQUENCE[(start_idx + offset) % len(YOGINI_SEQUENCE)]
+        span_days = full_years * item['years'] / TOTAL_CYCLE * year_length
+        end = major_end if offset == len(YOGINI_SEQUENCE) - 1 else cursor + timedelta(days=span_days)
+        if end <= birth:
+            cursor = end
+            continue
+        visible_start = birth if cursor < birth else cursor
+        row = {
+            'level': 'antardasha',
+            'planet': item['planet'],
+            'yogini': item['name'],
+            'lord': item['planet'],
+            'years': (end - visible_start).total_seconds() / (86400 * year_length),
+            'start_date': visible_start.isoformat(timespec='seconds'),
+            'end_date': end.isoformat(timespec='seconds'),
+        }
+        if cursor < birth:
+            row['unclipped_start_date'] = cursor.isoformat(timespec='seconds')
+        rows.append(row)
+        cursor = end
+    return rows
+
+
 def _calculate_moon_balanced_yogini(birth_info):
     """Goel Table I order, angular birth balance, explicit fixed-day year."""
     birth_dt = birth_info.get("birth_datetime")