fix: export no-auth test helpers from main module (#30)

The no-auth test helpers (test_agent_no_auth, test_agent_a2a_no_auth,
and their config constants) were added in PR #29 and exist in the
adcp.testing module, but were not exported from the main adcp module.

This meant users had to use:
  from adcp.testing import test_agent_no_auth

Instead of the expected:
  from adcp import test_agent_no_auth

This commit adds the missing exports to match the other test helpers
that are already exported.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: bokelley

src/adcp/__init__.py

@@ -23,13 +23,17 @@
 from adcp.testing import (
     CREATIVE_AGENT_CONFIG,
     TEST_AGENT_A2A_CONFIG,
+    TEST_AGENT_A2A_NO_AUTH_CONFIG,
     TEST_AGENT_MCP_CONFIG,
+    TEST_AGENT_MCP_NO_AUTH_CONFIG,
     TEST_AGENT_TOKEN,
     create_test_agent,
     creative_agent,
     test_agent,
     test_agent_a2a,
+    test_agent_a2a_no_auth,
     test_agent_client,
+    test_agent_no_auth,
 )
 from adcp.types.core import AgentConfig, Protocol, TaskResult, TaskStatus, WebhookMetadata
 from adcp.types.generated import (
@@ -161,12 +165,16 @@
     # Test helpers
     "test_agent",
     "test_agent_a2a",
+    "test_agent_no_auth",
+    "test_agent_a2a_no_auth",
     "creative_agent",
     "test_agent_client",
     "create_test_agent",
     "TEST_AGENT_TOKEN",
     "TEST_AGENT_MCP_CONFIG",
     "TEST_AGENT_A2A_CONFIG",
+    "TEST_AGENT_MCP_NO_AUTH_CONFIG",
+    "TEST_AGENT_A2A_NO_AUTH_CONFIG",
     "CREATIVE_AGENT_CONFIG",
     # Exceptions
     "ADCPError",