feat(chat): persistance bornee du brouillon custom chat par projet/layout (#182)

frontend/src/adapters/mock/index.ts

@@ -103,6 +103,8 @@ import type {
 import type {
   AgentChatHandle,
   AgentGateway,
+  ChatDraftScope,
+  ChatDraftSnapshot,
   ConversationGateway,
   ConversationPageRequest,
   ConversationDetails,
@@ -401,6 +403,8 @@ export class MockAgentGateway implements AgentGateway {
   private liveKindByAgent = new Map<string, "pty" | "structured">();
   /** Retained structured reply chunks per live chat session. */
   private chatScrollback = new Map<string, ReplyChunk[]>();
+  /** Persisted custom chat drafts keyed by project/layout/node. */
+  private chatDrafts = new Map<string, ChatDraftSnapshot>();
   private slashCommands: SlashCommand[] = [
     {
       name: "/help",
@@ -437,6 +441,10 @@ export class MockAgentGateway implements AgentGateway {
     return `${projectId}::${agentId}`;
   }
 
+  private chatDraftKey(scope: ChatDraftScope): string {
+    return `${scope.projectId}::${scope.layoutId}::${scope.nodeId}`;
+  }
+
   async listAgents(projectId: string): Promise<Agent[]> {
     return structuredClone(this.getAgents(projectId));
   }
@@ -985,6 +993,28 @@ export class MockAgentGateway implements AgentGateway {
     };
   }
 
+  async readChatDraft(scope: ChatDraftScope): Promise<ChatDraftSnapshot> {
+    return structuredClone(
+      this.chatDrafts.get(this.chatDraftKey(scope)) ?? { text: null, updatedAtMs: null },
+    );
+  }
+
+  async saveChatDraft(scope: ChatDraftScope, text: string): Promise<void> {
+    const key = this.chatDraftKey(scope);
+    if (text.length === 0) {
+      this.chatDrafts.delete(key);
+      return;
+    }
+    this.chatDrafts.set(key, {
+      text,
+      updatedAtMs: Date.now(),
+    });
+  }
+
+  async clearChatDraft(scope: ChatDraftScope): Promise<void> {
+    this.chatDrafts.delete(this.chatDraftKey(scope));
+  }
+
   async closeAgentChat(sessionId: string): Promise<void> {
     this.chatScrollback.delete(sessionId);
     for (const [agentId, liveSessionId] of this.liveSessionByAgent) {