feat: send repositories array to PostHog API for multi-repo tasks

Wire the client to send the new `repositories` array format when creating
multi-repo tasks. Single-repo tasks still use the legacy `repository` string
for backward compat.

- posthogClient.createTask: accepts `repositories` field
- TaskCreationSaga.createTask: detects additional repos, sends repositories
  array when multiple repos are present
- duplicateTask: preserves repositories array

Generated-By: PostHog Code
Task-Id: 230ec8e6-6781-43b4-ae30-ea24faa410dc

Author: richardsolomou

apps/code/src/renderer/api/posthogClient.ts

@@ -444,6 +444,7 @@ export class PostHogAPIClient {
           Task,
           | "title"
           | "repository"
+          | "repositories"
           | "json_schema"
           | "origin_product"
           | "signal_report"
@@ -490,7 +491,9 @@ export class PostHogAPIClient {
     return this.createTask({
       description: task.description ?? "",
       title: task.title,
-      repository: task.repository,
+      // Use repositories array if available, fall back to legacy field
+      repositories: task.repositories,
+      repository: task.repositories?.length ? undefined : task.repository,
       json_schema: task.json_schema,
       origin_product: task.origin_product,
       github_integration: task.github_integration,

apps/code/src/renderer/sagas/task/task-creation.ts

@@ -443,12 +443,37 @@ export class TaskCreationSaga extends Saga<
       }
     }
 
+    // Detect additional repos for multi-repo tasks
+    const additionalRepoNames: string[] = [];
+    if (input.additionalRepos) {
+      for (const repo of input.additionalRepos) {
+        const detected = await trpcClient.git.detectRepo.query({
+          directoryPath: repo.repoPath,
+        });
+        if (detected) {
+          additionalRepoNames.push(
+            `${detected.organization}/${detected.repository}`,
+          );
+        }
+      }
+    }
+
+    // Use repositories array when we have multiple repos
+    const hasMultipleRepos = repository && additionalRepoNames.length > 0;
+
     return this.step({
       name: "task_creation",
       execute: async () => {
         const result = await this.deps.posthogClient.createTask({
           description: input.content ?? "",
-          repository: repository ?? undefined,
+          // Send repositories array for multi-repo, legacy field for single-repo
+          repositories: hasMultipleRepos
+            ? [
+                { repository: repository! },
+                ...additionalRepoNames.map((r) => ({ repository: r })),
+              ]
+            : undefined,
+          repository: hasMultipleRepos ? undefined : (repository ?? undefined),
           github_integration:
             input.workspaceMode === "cloud"
               ? input.githubIntegrationId