feat(frontend): Add task branching API types and function

- Make contractId optional in CreateTaskRequest interface
- Add BranchTaskRequest interface with message, name, includeConversation fields
- Add BranchTaskResponse interface with task, messageCount, daemonId fields
- Add branchTask API function to call POST /api/v1/mesh/tasks/{id}/branch

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

1 files changed, 45 insertions, 2 deletions

diff --git a/makima/frontend/src/lib/api.ts b/makima/frontend/src/lib/api.ts
index 78e52cd..f34ba57 100644
--- a/makima/frontend/src/lib/api.ts
+++ b/makima/frontend/src/lib/api.ts
@@ -607,8 +607,8 @@ export interface TaskListResponse {
 }
 
 export interface CreateTaskRequest {
-  /** Contract this task belongs to (required) */
-  contractId: string;
+  /** Contract this task belongs to (optional - can be standalone) */
+  contractId?: string;
   name: string;
   description?: string;
   plan: string;
@@ -974,6 +974,49 @@ export async function listSubtasks(taskId: string): Promise<TaskListResponse> {
   return res.json();
 }
 
+// =============================================================================
+// Task Branching
+// =============================================================================
+
+/** Request to branch a task */
+export interface BranchTaskRequest {
+  /** Message to send to the new branched task */
+  message: string;
+  /** Optional name for the new task (defaults to "Branch of {original task name}") */
+  name?: string;
+  /** Whether to include conversation history from the source task */
+  includeConversation?: boolean;
+}
+
+/** Response from branching a task */
+export interface BranchTaskResponse {
+  /** The newly created task */
+  task: Task;
+  /** Number of conversation messages copied to the new task */
+  messageCount: number;
+  /** ID of the daemon assigned to the new task (null if not yet assigned) */
+  daemonId: string | null;
+}
+
+/**
+ * Branch a task to create a new task with the same state.
+ * Copies the worktree and optionally the conversation history.
+ */
+export async function branchTask(
+  taskId: string,
+  request: BranchTaskRequest
+): Promise<BranchTaskResponse> {
+  const res = await authFetch(`${API_BASE}/api/v1/mesh/tasks/${taskId}/branch`, {
+    method: "POST",
+    body: JSON.stringify(request),
+  });
+  if (!res.ok) {
+    const errorText = await res.text();
+    throw new Error(`Failed to branch task: ${errorText || res.statusText}`);
+  }
+  return res.json();
+}
+
 export async function listTaskEvents(
   taskId: string
 ): Promise<TaskEventListResponse> {