feat: migrate refimpls from draft-00 to draft-01 claim names

- Rename `par` to `pred` (predecessor) in types, serialization, tests
- Remove `pol`, `pol_decision` from core payload; move to `ect_ext`
- Remove `sub` from payload (not part of ECT spec)
- Update `typ` from `wimse-exec+jwt` to `exec+jwt` (accept both)
- Rename MaxParLength to MaxPredLength everywhere
- Update testdata, demos, READMEs with migration table
- All Go tests pass, all 56 Python tests pass (90% coverage)

refimpl/python/tests/test_create_extra.py

@@ -4,7 +4,7 @@ import time
 
 import pytest
 
-from ect import Payload, create, generate_key, CreateOptions, default_create_options, POL_DECISION_APPROVED
+from ect import Payload, create, generate_key, CreateOptions, default_create_options
 
 
 def test_default_create_options():
@@ -14,7 +14,7 @@ def test_default_create_options():
 
 def test_create_errors():
     key = generate_key()
-    p = Payload(iss="i", aud=["a"], iat=1, exp=2, jti="j", exec_act="e", par=[], pol="p", pol_decision=POL_DECISION_APPROVED)
+    p = Payload(iss="i", aud=["a"], iat=1, exp=2, jti="j", exec_act="e", pred=[])
     with pytest.raises(ValueError, match="KeyID|required"):
         create(p, key, CreateOptions(key_id=""))
     with pytest.raises((ValueError, TypeError, AttributeError)):
@@ -26,7 +26,7 @@ def test_create_optional_pol():
     now = int(time.time())
     p = Payload(
         iss="iss", aud=["a"], iat=now, exp=now + 3600,
-        jti="jti-nopol", exec_act="act", par=[],
+        jti="jti-nopol", exec_act="act", pred=[],
     )
     compact = create(p, key, CreateOptions(key_id="kid"))
     assert compact
@@ -34,7 +34,7 @@ def test_create_optional_pol():
 
 def test_create_validation_errors():
     key = generate_key()
-    base = dict(iss="i", aud=["a"], iat=1, exp=2, jti="j", exec_act="e", par=[])
+    base = dict(iss="i", aud=["a"], iat=1, exp=2, jti="j", exec_act="e", pred=[])
     with pytest.raises(ValueError, match="iss"):
         create(Payload(**{**base, "iss": ""}), key, CreateOptions(key_id="k"))
     with pytest.raises(ValueError, match="aud"):
@@ -43,16 +43,12 @@ def test_create_validation_errors():
         create(Payload(**{**base, "jti": ""}), key, CreateOptions(key_id="k"))
     with pytest.raises(ValueError, match="exec_act"):
         create(Payload(**{**base, "exec_act": ""}), key, CreateOptions(key_id="k"))
-    with pytest.raises(ValueError, match="pol and pol_decision"):
-        create(Payload(**{**base, "pol": "p", "pol_decision": ""}), key, CreateOptions(key_id="k"))
-    with pytest.raises(ValueError, match="pol_decision"):
-        create(Payload(**{**base, "pol": "p", "pol_decision": "bad"}), key, CreateOptions(key_id="k"))
 
 
 def test_create_ext_compensation_reason_requires_required():
     key = generate_key()
     p = Payload(
-        iss="i", aud=["a"], iat=1, exp=2, jti="j", exec_act="e", par=[],
+        iss="i", aud=["a"], iat=1, exp=2, jti="j", exec_act="e", pred=[],
         ext={"compensation_reason": "rollback", "compensation_required": False},
     )
     with pytest.raises(ValueError, match="compensation_required"):
@@ -61,7 +57,7 @@ def test_create_ext_compensation_reason_requires_required():
 
 def test_create_zero_expiry_uses_default():
     key = generate_key()
-    p = Payload(iss="i", aud=["a"], iat=0, exp=0, jti="j", exec_act="e", par=[])
+    p = Payload(iss="i", aud=["a"], iat=0, exp=0, jti="j", exec_act="e", pred=[])
     compact = create(p, key, CreateOptions(key_id="k", default_expiry_sec=300))
     assert compact
     # create() works on a copy; decode the token to verify defaults were applied
@@ -73,17 +69,17 @@ def test_create_zero_expiry_uses_default():
 def test_create_validate_uuids_rejects_non_uuid_jti():
     key = generate_key()
     now = int(time.time())
-    p = Payload(iss="i", aud=["a"], iat=now, exp=now + 3600, jti="not-a-uuid", exec_act="e", par=[])
+    p = Payload(iss="i", aud=["a"], iat=now, exp=now + 3600, jti="not-a-uuid", exec_act="e", pred=[])
     with pytest.raises(ValueError, match="jti must be UUID"):
         create(p, key, CreateOptions(key_id="k", validate_uuids=True))
 
 
-def test_create_max_par_length():
+def test_create_max_pred_length():
     key = generate_key()
     now = int(time.time())
-    p = Payload(iss="i", aud=["a"], iat=now, exp=now + 3600, jti="550e8400-e29b-41d4-a716-446655440000", exec_act="e", par=["p1", "p2"])
-    with pytest.raises(ValueError, match="par exceeds max length"):
-        create(p, key, CreateOptions(key_id="k", max_par_length=1))
+    p = Payload(iss="i", aud=["a"], iat=now, exp=now + 3600, jti="550e8400-e29b-41d4-a716-446655440000", exec_act="e", pred=["p1", "p2"])
+    with pytest.raises(ValueError, match="pred exceeds max length"):
+        create(p, key, CreateOptions(key_id="k", max_pred_length=1))
 
 
 def test_create_ext_size_rejected():
@@ -91,7 +87,7 @@ def test_create_ext_size_rejected():
     key = generate_key()
     now = int(time.time())
     p = Payload(
-        iss="i", aud=["a"], iat=now, exp=now + 3600, jti="550e8400-e29b-41d4-a716-446655440000", exec_act="e", par=[],
+        iss="i", aud=["a"], iat=now, exp=now + 3600, jti="550e8400-e29b-41d4-a716-446655440000", exec_act="e", pred=[],
         ext={"x": "y" * (EXT_MAX_SIZE - 5)},
     )
     with pytest.raises(ValueError, match="ext exceeds max size"):