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>

docs/agent-runner-pluginization/PHASE0_INTEGRATION_RECORD.md

@@ -0,0 +1,63 @@
+# Agent Runner Pluginization Phase 0 Integration Test Record
+
+## Test Summary
+
+**Status**: PASSED
+
+**Date**: 2026-05-10 10:09
+
+## Test Configuration
+
+- **LangBot Branch**: feat/agent-runner-plugin
+- **SDK Branch**: feat/agent-runner-plugin
+- **Runner Repo**: langbot-agent-runner (new)
+
+## Test Scenario
+
+- **Selected Runner**: `plugin:langbot/local-agent/default`
+- **Input**: `1`
+- **Expected Output**: `[stub] Echo: 1`
+- **Actual Output**: `[stub] Echo: 1`
+
+## Verified Chain
+
+```
+Frontend selects plugin:langbot/local-agent/default
+  -> LangBot pipeline
+  -> AgentRunOrchestrator
+  -> SDK runtime RUN_AGENT
+  -> langbot-agent-runner/local-agent DefaultAgentRunner
+  -> AgentRunResult
+  -> LangBot response
+```
+
+## Key Components Verified
+
+### LangBot Host
+- AgentRunOrchestrator resolves runner ID via ConfigMigration
+- AgentRunContextBuilder builds SDK v1 context
+- AgentResultNormalizer normalizes SDK v1 results
+- ChatMessageHandler delegates to orchestrator (single resp_message_id, streaming pop/append)
+
+### SDK Runtime
+- RUN_AGENT action dispatches to plugin runner
+- AgentRunner component manifest parsing
+- LIST_AGENT_RUNNERS returns runner metadata
+
+### langbot-agent-runner Plugin
+- DefaultAgentRunner stub implementation
+- AgentRunner manifest with protocol_version, capabilities, permissions
+- Echo response validates SDK v1 result format
+
+## Next Steps (Phase 1)
+
+1. Implement real Dify runner (external API runner validation)
+2. Update frontend to save `ai.runner.id` + `ai.runner_config`
+3. Add persistence migration for old config format
+4. Update pipeline templates
+5. Add proxy action secondary permission validation
+
+## Related Documents
+
+- [IMPLEMENTATION_PLAN.md](./IMPLEMENTATION_PLAN.md)
+- [OFFICIAL_RUNNER_PLUGINS.md](./OFFICIAL_RUNNER_PLUGINS.md)