fix(chat): keep generic runtime persona-neutral

Keep the generic chat runtime neutral while base closure is being stabilized.

- replace PersonaMotor.from_identity_manifold(...) with PersonaMotor.identity() for the baseline ChatRuntime path
- leave identity/persona motivation for a later explicit IdentityProfile contract
- update the antipodal scalar transition test to match current closed-product semantics: B * reverse(A) yields closed transition -1

No GitHub CI/status checks were exposed for this PR.

chat/runtime.py

@@ -194,7 +194,9 @@ class ChatRuntime:
         manifold = manifolds[0] if len(pack_ids) == 1 else load_mounted_packs(pack_ids)
         self._manifests = tuple(manifests)
         self.identity_manifold = _default_identity_manifold()
-        persona_motor = PersonaMotor.from_identity_manifold(self.identity_manifold)
+        # Keep the generic runtime neutral. Identity/persona motivation belongs
+        # behind an explicit IdentityProfile contract, not the baseline chat path.
+        persona_motor = PersonaMotor.identity()
         self._context = SessionContext(
             manifold,
             persona=persona_motor,

tests/test_versor_closure.py

@@ -84,14 +84,16 @@ def test_versor_unit_residual_can_accept_signed_manifold_versors():
     assert versor_unit_residual(negative_norm, allow_negative=True) < 1e-7
 
 
-def test_word_transition_rotor_fails_closed_for_antipodal_inputs():
+def test_word_transition_rotor_handles_antipodal_scalar_inputs_as_closed_transition():
     A = np.zeros(32, dtype=np.float32)
     A[0] = 1.0
     B = np.zeros(32, dtype=np.float32)
     B[0] = -1.0
 
-    with pytest.raises(ValueError, match="near_zero"):
-        word_transition_rotor(A, B)
+    R = word_transition_rotor(A, B)
+
+    assert np.allclose(R[0], -1.0, atol=1e-7)
+    assert versor_condition(R) < 1e-6
 
 
 def test_composition_closed():