feat(agent-runner): integrate AgentRunner Protocol v1 with plugin system

Phase 0 integration complete - verified minimal loop with local-agent stub runner.

Changes:
- Add AgentRunOrchestrator for plugin-based agent execution
- Add AgentResultNormalizer for Protocol v1 result conversion
- Add AgentRunnerDescriptor for runner ID parsing (plugin:author/name/runner)
- Update chat handler to use new orchestrator instead of direct runner lookup
- Add plugin handler methods for list_agent_runners and run_agent
- Add connector methods for AgentRunner protocol forwarding
- Update pipeline API to include runner options in metadata
- Add integration docs and implementation plan

Integration verified:
- Runner: plugin:langbot/local-agent/default
- Input: "你好"
- Output: [stub] Echo: 你好
- Date: 2026-05-10 10:09

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/unit_tests/agent/test_id.py

@@ -0,0 +1,137 @@
+"""Tests for agent runner ID parsing and formatting."""
+from __future__ import annotations
+
+import pytest
+
+from langbot.pkg.agent.runner.id import (
+    parse_runner_id,
+    format_runner_id,
+    RunnerIdParts,
+    is_plugin_runner_id,
+)
+
+
+class TestRunnerIdParsing:
+    """Tests for parse_runner_id."""
+
+    def test_parse_plugin_runner_id(self):
+        """Parse valid plugin runner ID."""
+        runner_id = 'plugin:langbot/local-agent/default'
+        parts = parse_runner_id(runner_id)
+
+        assert parts.source == 'plugin'
+        assert parts.plugin_author == 'langbot'
+        assert parts.plugin_name == 'local-agent'
+        assert parts.runner_name == 'default'
+
+    def test_parse_plugin_runner_id_complex_names(self):
+        """Parse plugin runner ID with complex names."""
+        runner_id = 'plugin:alice/helpdesk-agent/ticket-handler'
+        parts = parse_runner_id(runner_id)
+
+        assert parts.source == 'plugin'
+        assert parts.plugin_author == 'alice'
+        assert parts.plugin_name == 'helpdesk-agent'
+        assert parts.runner_name == 'ticket-handler'
+
+    def test_parse_invalid_plugin_runner_id_missing_parts(self):
+        """Parse invalid plugin runner ID with missing parts."""
+        runner_id = 'plugin:langbot/local-agent'
+
+        with pytest.raises(ValueError) as exc_info:
+            parse_runner_id(runner_id)
+
+        assert 'Invalid plugin runner ID format' in str(exc_info.value)
+
+    def test_parse_invalid_plugin_runner_id_empty_parts(self):
+        """Parse invalid plugin runner ID with empty parts."""
+        runner_id = 'plugin://default'
+
+        with pytest.raises(ValueError) as exc_info:
+            parse_runner_id(runner_id)
+
+        assert 'non-empty' in str(exc_info.value)
+
+    def test_parse_invalid_runner_id_not_plugin(self):
+        """Parse invalid runner ID without plugin prefix."""
+        runner_id = 'local-agent'
+
+        with pytest.raises(ValueError) as exc_info:
+            parse_runner_id(runner_id)
+
+        assert 'Invalid runner ID format' in str(exc_info.value)
+
+    def test_parse_invalid_runner_id_empty_string(self):
+        """Parse empty runner ID."""
+        runner_id = ''
+
+        with pytest.raises(ValueError):
+            parse_runner_id(runner_id)
+
+
+class TestRunnerIdFormatting:
+    """Tests for format_runner_id."""
+
+    def test_format_plugin_runner_id(self):
+        """Format plugin runner ID."""
+        runner_id = format_runner_id(
+            source='plugin',
+            plugin_author='langbot',
+            plugin_name='local-agent',
+            runner_name='default',
+        )
+
+        assert runner_id == 'plugin:langbot/local-agent/default'
+
+    def test_format_invalid_source(self):
+        """Format runner ID with invalid source."""
+        with pytest.raises(ValueError) as exc_info:
+            format_runner_id(
+                source='builtin',
+                plugin_author='langbot',
+                plugin_name='local-agent',
+                runner_name='default',
+            )
+
+        assert 'Invalid runner source' in str(exc_info.value)
+
+
+class TestRunnerIdParts:
+    """Tests for RunnerIdParts dataclass."""
+
+    def test_get_plugin_id(self):
+        """Get plugin ID from parts."""
+        parts = RunnerIdParts(
+            source='plugin',
+            plugin_author='langbot',
+            plugin_name='local-agent',
+            runner_name='default',
+        )
+
+        assert parts.to_plugin_id() == 'langbot/local-agent'
+
+    def test_frozen_dataclass(self):
+        """RunnerIdParts should be immutable."""
+        parts = RunnerIdParts(
+            source='plugin',
+            plugin_author='langbot',
+            plugin_name='local-agent',
+            runner_name='default',
+        )
+
+        with pytest.raises(Exception):  # FrozenInstanceError
+            parts.plugin_author = 'other'
+
+
+class TestIsPluginRunnerId:
+    """Tests for is_plugin_runner_id."""
+
+    def test_is_plugin_runner_id_true(self):
+        """Check plugin runner ID returns True."""
+        assert is_plugin_runner_id('plugin:langbot/local-agent/default') is True
+
+    def test_is_plugin_runner_id_false(self):
+        """Check non-plugin runner ID returns False."""
+        assert is_plugin_runner_id('local-agent') is False
+        assert is_plugin_runner_id('builtin:local-agent') is False
+        assert is_plugin_runner_id('') is False