feat(plugins): seam slash-commands contribuées par plugin via callback — #165 (QA verte)

Permet à un plugin de contribuer des commandes slash adossées à une callback,
transitant par le registry/contrat unifié (#162) :

- sdk/IdeaSDK: manifeste contributes.slashCommands (déclaratif) — pointer bumpé.
- domain: source Plugin étendue + effet PluginCallback (la commande ne
  s'exécute pas directement : elle renvoie une référence à la callback du plugin).
- application: registration des commandes plugin dans le registry + exécution
  renvoyant l'effet PluginCallback ; métadonnées UI suffisantes pour l'autocomplete.
- backend + app-tauri: DTO + commandes Tauri listant/invoquant les commandes plugin.
- frontend (contrat): types adapters/domain/ports/mock pour pluginCallback et
  l'invocation avec arguments.

L'exécution effective de la callback côté runtime UI est livrée par #166.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/adapters/agent.test.ts

@@ -248,7 +248,7 @@ describe("TauriAgentGateway invoke payloads", () => {
     });
 
     expect(invoke).toHaveBeenCalledWith("execute_slash_command", {
-      request: { name: "/clean", sessionId: "chat-session-1" },
+      request: { name: "/clean", sessionId: "chat-session-1", arguments: [] },
     });
     expect(out.effect.kind).toBe("cleanConversation");
   });

frontend/src/adapters/agent.ts

@@ -286,12 +286,13 @@ export class TauriAgentGateway implements AgentGateway {
 
   async executeSlashCommand(
     name: string,
-    options: { sessionId?: string | null } = {},
+    options: { sessionId?: string | null; arguments?: unknown[] } = {},
   ): Promise<ExecuteSlashCommandResult> {
     return invoke<ExecuteSlashCommandResult>("execute_slash_command", {
       request: {
         name,
         sessionId: options.sessionId ?? null,
+        arguments: options.arguments ?? [],
       },
     });
   }

frontend/src/adapters/mock/index.ts

@@ -906,7 +906,7 @@ export class MockAgentGateway implements AgentGateway {
 
   async executeSlashCommand(
     name: string,
-    options: { sessionId?: string | null } = {},
+    options: { sessionId?: string | null; arguments?: unknown[] } = {},
   ): Promise<ExecuteSlashCommandResult> {
     const normalized = name.trim().startsWith("/") ? name.trim() : `/${name.trim()}`;
     const command = this.slashCommands.find((item) => item.name === normalized);
@@ -951,6 +951,18 @@ export class MockAgentGateway implements AgentGateway {
         },
       };
     }
+    if (command.plugin) {
+      return {
+        command: structuredClone(command),
+        effect: {
+          kind: "pluginCallback",
+          pluginId: command.plugin.pluginId,
+          commandId: command.plugin.commandId,
+          sessionId: options.sessionId ?? undefined,
+          arguments: structuredClone(options.arguments ?? []),
+        },
+      };
+    }
     return {
       command: structuredClone(command),
       effect: {

frontend/src/domain/index.ts

@@ -1698,12 +1698,23 @@ export interface SlashCommand {
   availability: SlashCommandAvailability;
   source: SlashCommandSource;
   native?: NativeSlashCommand;
+  plugin?: {
+    pluginId: string;
+    commandId: string;
+  };
 }
 
 export type SlashCommandEffect =
   | { kind: "help"; commands: SlashCommand[] }
   | { kind: "cleanConversation"; sessionId: string; clearedChunks: number }
-  | { kind: "profileSwitch"; sessionId: string };
+  | { kind: "profileSwitch"; sessionId: string }
+  | {
+      kind: "pluginCallback";
+      pluginId: string;
+      commandId: string;
+      sessionId?: string;
+      arguments: unknown[];
+    };
 
 export interface ExecuteSlashCommandResult {
   command: SlashCommand;
@@ -1844,6 +1855,7 @@ export interface PluginUninstallResult {
 export interface PluginContributionDto {
   menus: PluginTopLevelMenuContribution[];
   menuItems: PluginMenuItemContribution[];
+  slashCommands?: PluginSlashCommandContribution[];
   layouts: PluginLayoutContribution[];
   mcpServers: PluginMcpServerSummary[];
 }
@@ -2125,6 +2137,15 @@ export interface PluginMenuItemContribution {
   when?: string;
 }
 
+/** Manifest declaration of a plugin-backed slash command. */
+export interface PluginSlashCommandContribution {
+  name: string;
+  shortDescription: string;
+  command: string;
+  requiresConfirmation?: boolean;
+  when?: string;
+}
+
 /** A menu item resolved for rendering — enablement already evaluated (carnet §7.2). */
 export interface ResolvedPluginMenuItem {
   id: string;

frontend/src/ports/index.ts

@@ -315,7 +315,7 @@ export interface AgentGateway {
   /** Executes a selected slash command and returns the planned UI effect. */
   executeSlashCommand?(
     name: string,
-    options?: { sessionId?: string | null },
+    options?: { sessionId?: string | null; arguments?: unknown[] },
   ): Promise<ExecuteSlashCommandResult>;
   /** Interrupts only the current turn of a live structured session. */
   cancelAgentChat?(sessionId: string): Promise<void>;