feat(frontend): système de plugins — runtime, menus, layouts custom (#43)

Lots F1-F4 : runtime de chargement/registre plugin, extension des menus
existants, panneau de gestion des plugins, types de layout custom
(sélecteur, fallback, cellule dédiée) branchés sur le port plugin.
Suite npm typecheck/test verte (947/947).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/adapters/plugin.ts

@@ -0,0 +1,58 @@
+/**
+ * Tauri adapter for {@link PluginGateway} (ticket #43, F1).
+ *
+ * Commands use snake_case (Tauri convention); payload keys are camelCase,
+ * consistent with the other adapters in this directory. Command names and
+ * envelope match the carnet §5 exactly — no contract improvised here.
+ *
+ * NOTE: The Tauri commands wired here are defined in the backend `app-tauri`
+ * crate (lots B1-B4, in progress in parallel on this branch). The mock gateway
+ * covers tests and offline dev today.
+ */
+
+import { invoke } from "@tauri-apps/api/core";
+
+import type {
+  PluginAdmin,
+  PluginInstallResult,
+  PluginReview,
+  PluginRuntimeContributionCatalog,
+  PluginUninstallResult,
+} from "@/domain";
+import type { PluginGateway, ReviewPluginPackageInput } from "@/ports";
+
+export class TauriPluginGateway implements PluginGateway {
+  listPlugins(): Promise<PluginAdmin[]> {
+    return invoke<PluginAdmin[]>("plugin_list_plugins");
+  }
+
+  reviewPackage(input: ReviewPluginPackageInput): Promise<PluginReview> {
+    return invoke<PluginReview>("plugin_review_package", {
+      request: { sourceKind: input.sourceKind, path: input.path },
+    });
+  }
+
+  installFromArchive(path: string): Promise<PluginInstallResult> {
+    return invoke<PluginInstallResult>("plugin_install_from_archive", { path });
+  }
+
+  installFromDirectory(path: string): Promise<PluginInstallResult> {
+    return invoke<PluginInstallResult>("plugin_install_from_directory", { path });
+  }
+
+  setEnabled(pluginId: string, enabled: boolean): Promise<PluginAdmin> {
+    return invoke<PluginAdmin>("plugin_set_enabled", { pluginId, enabled });
+  }
+
+  uninstall(pluginId: string): Promise<PluginUninstallResult> {
+    return invoke<PluginUninstallResult>("plugin_uninstall", { pluginId });
+  }
+
+  listRuntimeContributions(): Promise<PluginRuntimeContributionCatalog> {
+    return invoke<PluginRuntimeContributionCatalog>("plugin_list_runtime_contributions");
+  }
+
+  async openPluginsFolder(pluginId?: string): Promise<void> {
+    await invoke("plugin_open_plugins_folder", { pluginId: pluginId ?? null });
+  }
+}