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/go-lang/ect/config_test.go

@@ -0,0 +1,79 @@
+package ect
+
+import (
+	"os"
+	"testing"
+	"time"
+)
+
+func TestDefaultConfig(t *testing.T) {
+	c := DefaultConfig()
+	if c.IATMaxAge != 15*time.Minute {
+		t.Errorf("IATMaxAge: got %v", c.IATMaxAge)
+	}
+	if c.JTIReplaySize != 0 {
+		t.Errorf("JTIReplaySize: got %d", c.JTIReplaySize)
+	}
+}
+
+func TestLoadConfigFromEnv(t *testing.T) {
+	os.Setenv(EnvIATMaxAgeMinutes, "20")
+	os.Setenv(EnvJTIReplayCacheSize, "1000")
+	os.Setenv(EnvIATMaxFutureSec, "45")
+	os.Setenv(EnvDefaultExpiryMin, "12")
+	os.Setenv(EnvJTIReplayTTLMin, "90")
+	defer func() {
+		os.Unsetenv(EnvIATMaxAgeMinutes)
+		os.Unsetenv(EnvJTIReplayCacheSize)
+		os.Unsetenv(EnvIATMaxFutureSec)
+		os.Unsetenv(EnvDefaultExpiryMin)
+		os.Unsetenv(EnvJTIReplayTTLMin)
+	}()
+	c := LoadConfigFromEnv()
+	if c.IATMaxAge != 20*time.Minute {
+		t.Errorf("IATMaxAge from env: got %v", c.IATMaxAge)
+	}
+	if c.JTIReplaySize != 1000 {
+		t.Errorf("JTIReplaySize from env: got %d", c.JTIReplaySize)
+	}
+	if c.IATMaxFuture != 45*time.Second {
+		t.Errorf("IATMaxFuture: got %v", c.IATMaxFuture)
+	}
+	if c.DefaultExpiry != 12*time.Minute {
+		t.Errorf("DefaultExpiry: got %v", c.DefaultExpiry)
+	}
+	if c.JTIReplayTTL != 90*time.Minute {
+		t.Errorf("JTIReplayTTL: got %v", c.JTIReplayTTL)
+	}
+}
+
+func TestLoadConfigFromEnv_invalidInt(t *testing.T) {
+	os.Setenv(EnvIATMaxAgeMinutes, "bad")
+	defer os.Unsetenv(EnvIATMaxAgeMinutes)
+	c := LoadConfigFromEnv()
+	if c.IATMaxAge != 15*time.Minute {
+		t.Errorf("invalid int should keep default: got %v", c.IATMaxAge)
+	}
+}
+
+func TestConfig_CreateOptions(t *testing.T) {
+	c := DefaultConfig()
+	opts := c.CreateOptions("my-kid")
+	if opts.KeyID != "my-kid" {
+		t.Errorf("KeyID: got %q", opts.KeyID)
+	}
+	if opts.DefaultExpiry != c.DefaultExpiry {
+		t.Errorf("DefaultExpiry: got %v", opts.DefaultExpiry)
+	}
+}
+
+func TestConfig_VerifyOptions(t *testing.T) {
+	c := DefaultConfig()
+	opts := c.VerifyOptions()
+	if opts.IATMaxAge != c.IATMaxAge {
+		t.Errorf("IATMaxAge: got %v", opts.IATMaxAge)
+	}
+	if opts.DAG.ClockSkewTolerance != DefaultClockSkewTolerance {
+		t.Errorf("DAG.ClockSkewTolerance: got %d", opts.DAG.ClockSkewTolerance)
+	}
+}