Restructure refimpl into go-lang and python subdirectories

Move Go reference implementation to refimpl/go-lang/ and add new
Python reference implementation in refimpl/python/. Update build.sh
with renamed draft and simplified tool paths.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

refimpl/python/tests/test_create.py

@@ -0,0 +1,77 @@
+"""Tests for ECT creation and roundtrip."""
+
+import json
+import os
+import time
+
+import pytest
+
+from ect import (
+    Payload,
+    create,
+    generate_key,
+    CreateOptions,
+    verify,
+    VerifyOptions,
+    POL_DECISION_APPROVED,
+)
+
+
+def test_create_roundtrip():
+    key = generate_key()
+    now = int(time.time())
+    payload = Payload(
+        iss="spiffe://example.com/agent/a",
+        aud=["spiffe://example.com/agent/b"],
+        iat=now,
+        exp=now + 600,
+        jti="e4f5a6b7-c8d9-0123-ef01-234567890abc",
+        exec_act="review_spec",
+        par=[],
+        pol="spec_review_policy_v2",
+        pol_decision=POL_DECISION_APPROVED,
+    )
+    compact = create(payload, key, CreateOptions(key_id="agent-a-key-1"))
+    assert compact
+
+    def resolver(kid):
+        if kid == "agent-a-key-1":
+            return key.public_key()
+        return None
+
+    opts = VerifyOptions(
+        verifier_id="spiffe://example.com/agent/b",
+        resolve_key=resolver,
+        now=now,
+    )
+    parsed = verify(compact, opts)
+    assert parsed.payload.jti == payload.jti
+    assert parsed.payload.exec_act == payload.exec_act
+
+
+def test_create_with_test_vector():
+    path = os.path.join(os.path.dirname(__file__), "..", "testdata", "valid_root_ect_payload.json")
+    if not os.path.exists(path):
+        pytest.skip(f"test vector not found: {path}")
+    with open(path) as f:
+        data = json.load(f)
+    payload = Payload.from_claims(data)
+    key = generate_key()
+    now = int(time.time())
+    payload.iat = now
+    payload.exp = now + 600
+
+    compact = create(payload, key, CreateOptions(key_id="test-kid"))
+    assert compact
+
+    def resolver(kid):
+        if kid == "test-kid":
+            return key.public_key()
+        return None
+
+    opts = VerifyOptions(
+        verifier_id=payload.aud[0],
+        resolve_key=resolver,
+        now=now,
+    )
+    verify(compact, opts)