semi implemented and features implemented save checkpoint

docs/features/unchecked/plugin/plugin-sandbox.md

@@ -0,0 +1,25 @@
+# Plugin Sandbox (Process Isolation)
+
+## Module
+Plugin
+
+## Status
+IMPLEMENTED
+
+## Description
+Process-level plugin sandboxing with gRPC communication bridge for secure out-of-process plugin execution.
+
+## Implementation Details
+- **PluginTrustLevel**: `src/Plugin/StellaOps.Plugin.Abstractions/PluginTrustLevel.cs` -- enum: BuiltIn (in-process full access), Trusted (isolated monitored), Untrusted (sandboxed restricted)
+- **PluginHost trust routing**: `src/Plugin/StellaOps.Plugin.Host/PluginHost.cs` -- DetermineTrustLevel routes plugins to BuiltIn (matching BuiltInPluginIds), Trusted (matching TrustedPluginIds/TrustedVendors), or Untrusted (default); trust level passed to loader and context factory for execution environment selection
+- **PluginLifecycleManager**: `src/Plugin/StellaOps.Plugin.Host/Lifecycle/PluginLifecycleManager.cs` -- manages state transitions with PluginStateMachine
+- **PluginStateMachine**: `src/Plugin/StellaOps.Plugin.Host/Lifecycle/PluginStateMachine.cs` -- enforces valid lifecycle state transitions
+- **PluginHealthMonitor**: `src/Plugin/StellaOps.Plugin.Host/Health/PluginHealthMonitor.cs` -- periodic health checks with HealthChanged events
+- **Source**: Feature matrix scan
+
+## E2E Test Plan
+- [ ] Verify untrusted plugins execute in sandboxed process with restricted capabilities
+- [ ] Test trusted plugins run isolated but with monitoring
+- [ ] Verify built-in plugins run in-process with full access
+- [ ] Test health monitoring detects unhealthy sandboxed plugins
+- [ ] Verify process isolation prevents sandbox escape