fix(engine): dispositor cycles are not collapsed to one planet; dasa convergence drops uncalibrated probabilities (upstream e9beae6b)

final_dispositor_from_chain and its regression test are upstream
yinduzhanxing e9beae6b; probability is None with probability_basis. The
Narayana convergence additions of that commit are out of scope.
TASK-upstream-sync4-20261002 T7.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N4f2nya58RoRu4yEmJgRGE

tests/test_dispositor_cycle_resolution.py

@@ -0,0 +1,38 @@
+"""Do not collapse a directed dispositor cycle into an arbitrary terminal."""
+import ast
+from pathlib import Path
+
+
+def resolver():
+    # Isolate the pure function without importing the large CLI and adapters.
+    source = Path(__file__).parents[1] / 'scripts/jyotish_engine.py'
+    tree = ast.parse(source.read_text())
+    node = next(n for n in tree.body if isinstance(n, ast.FunctionDef)
+                and n.name == 'final_dispositor_from_chain')
+    namespace = {}
+    exec(compile(ast.Module(body=[node], type_ignores=[]), str(source), 'exec'), namespace)
+    return namespace[node.name]
+
+
+def chain(*names):
+    return [{'planet':a,'dispositor':b} for a,b in zip(names,names[1:])]
+
+
+def test_cycle_rotation_and_leading_planet():
+    f = resolver()
+    expected = 'Cycle: Jupiter -> Mercury -> Jupiter'
+    assert f(chain('Mercury','Jupiter','Mercury')) == expected
+    assert f(chain('Jupiter','Mercury','Jupiter')) == expected
+    assert f(chain('Venus','Jupiter','Mercury','Jupiter')) == expected
+
+
+def test_terminal_and_incomplete_are_distinct():
+    f = resolver()
+    assert f(chain('Sun','Mars','Saturn','Saturn')) == 'Saturn'
+    assert f(chain('Sun','Mars')) is None
+    assert f([]) is None
+    assert f(chain('Sun','Mars') + chain('Venus','Venus')) is None
+
+
+def test_three_body_cycle_preserves_direction():
+    assert resolver()(chain('Sun','Mars','Moon','Sun')) == 'Cycle: Mars -> Moon -> Sun -> Mars'