feat(sdk,plugins): ajoute capability tooling et services runtime publics (workspace/terminal/tasks)

- capability manifeste tooling supportée backend + transport runtime catalog
- ctx.services publique côté SDK/runtime, gated par tooling
- surface honnête: workspace, terminal, et tasks en observation/contrôle uniquement
- docs/exemple/tests mis à jour
- QA PASS sur feature/sdk-plugin-tooling-build-debug-surface

crates/domain/src/plugin.rs

@@ -284,6 +284,8 @@ pub enum PluginCapability {
     Ui,
     /// External MCP server declarations.
     Mcp,
+    /// Public tooling/build/debug services.
+    Tooling,
 }
 
 /// Plugin command id.
@@ -678,4 +680,17 @@ mod tests {
         assert!(!PluginLifecycleState::PendingUninstall.is_runtime_active());
         assert!(PluginLifecycleState::Enabled.is_runtime_active());
     }
+
+    #[test]
+    fn plugin_capabilities_serialize_public_manifest_names() {
+        assert_eq!(
+            serde_json::to_value([
+                PluginCapability::Ui,
+                PluginCapability::Mcp,
+                PluginCapability::Tooling
+            ])
+            .unwrap(),
+            serde_json::json!(["ui", "mcp", "tooling"])
+        );
+    }
 }