feat(model-server): wizard V2 config modèles locaux — source, options structurées & preview

Refonte UX du wizard de configuration des modèles locaux du serveur
llama.cpp intégré, alignée sur la source Hugging Face et les options backend.

- choix de source sans jargon (chemin local .gguf vs dépôt Hugging Face) ;
- champs structurés -ngl (gpu_layers), -c (context_size), --jinja, --host ;
- zone d'arguments libres avec alerte sur les flags réservés ;
- preview de la commande via le backend (previewModelServerCommand, debounced) ;
- gateway/ports et mock adaptés au contrat V2.

QA : Vitest 22 verts, tsc/build OK.

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

frontend/src/adapters/mock/index.ts

@@ -24,6 +24,7 @@ import type {
   LayoutOperation,
   LayoutTree,
   LocalModelServerConfig,
+  ModelServerCommandPreview,
   Memory,
   MemoryIndexEntry,
   MemoryLink,
@@ -1284,6 +1285,44 @@ export class MockModelServerGateway implements ModelServerGateway {
     this.servers = this.servers.filter((s) => s.id !== serverId);
   }
 
+  async previewModelServerCommand(
+    config: LocalModelServerConfig,
+  ): Promise<ModelServerCommandPreview> {
+    // Mirror of the backend `LlamaCppRuntime::build_argv` (order matters), kept
+    // deliberately simple: it exists so the UI preview flow is testable, never
+    // as the source of truth (production uses the real backend command).
+    if (!config.modelSource) {
+      const err: GatewayError = {
+        code: "INVALID",
+        message: "model.source missing",
+      };
+      throw err;
+    }
+    const command =
+      config.binaryPath && config.binaryPath.trim().length > 0
+        ? config.binaryPath
+        : "llama-server";
+    const args: string[] = [];
+    if (config.modelSource.type === "localPath") {
+      args.push("--model", config.modelSource.path);
+    } else {
+      args.push("-hf", config.modelSource.repo);
+    }
+    args.push("--port", String(config.port), "--host", config.host);
+    if (config.gpuLayers !== undefined) {
+      args.push("-ngl", String(config.gpuLayers));
+    }
+    if (config.contextSize !== undefined) {
+      args.push("-c", String(config.contextSize));
+    }
+    if (config.jinja) args.push("--jinja");
+    args.push(...config.args);
+    const display = [command, ...args]
+      .map((part) => (/\s/.test(part) ? `'${part}'` : part))
+      .join(" ");
+    return { command, args, display };
+  }
+
   /** Test hook: mark a server id as still referenced (delete then rejects). */
   markInUse(serverId: string): void {
     this.inUse.add(serverId);

frontend/src/adapters/modelServer.ts

@@ -9,7 +9,10 @@
 
 import { invoke } from "@tauri-apps/api/core";
 
-import type { LocalModelServerConfig } from "@/domain";
+import type {
+  LocalModelServerConfig,
+  ModelServerCommandPreview,
+} from "@/domain";
 import type { ModelServerGateway } from "@/ports";
 
 export class TauriModelServerGateway implements ModelServerGateway {
@@ -28,4 +31,14 @@ export class TauriModelServerGateway implements ModelServerGateway {
   async deleteModelServer(serverId: string): Promise<void> {
     await invoke("delete_model_server", { serverId });
   }
+
+  previewModelServerCommand(
+    config: LocalModelServerConfig,
+  ): Promise<ModelServerCommandPreview> {
+    // `preview_model_server_command` takes the config directly (no `request`
+    // wrapper), unlike `save_model_server`.
+    return invoke<ModelServerCommandPreview>("preview_model_server_command", {
+      config,
+    });
+  }
 }