[FEATURE] Allow custom branch name for isolation: worktree in Task tool

Problem Statement

When using isolation: "worktree" in the Task tool to spawn agents in isolated git worktrees, the branch name is automatically generated as worktree-agent-{hash} and cannot be configured. The worktree path is also not configurable.

This makes it difficult to:

1. Identify which worktree belongs to which task (branch names are opaque hashes)
2. Integrate with existing branch naming conventions (e.g., feature/issue-123)
3. Resume work on a specific worktree after session interruption
4. Manage worktrees manually (e.g., git worktree list shows only hash-based names)

Additionally, background team members spawned with isolation: "worktree" still have their pwd set to the main repository, meaning the isolation doesn't actually take effect for them.

Proposed Solution

Add optional parameters to the Task tool's isolation: "worktree" mode:

• worktree_branch: Custom branch name for the worktree (e.g., "S1-13-qq-channel")
• worktree_path: Custom path for the worktree directory

Example:

{
  "isolation": "worktree",
  "worktree_branch": "feature/my-task",
  "worktree_path": "../worktrees/my-task"
}

Also ensure that background team members correctly inherit the worktree working directory.

Priority

Medium

Feature Category

Task tool / Agent Teams / Git integration

Environment

• Claude Code version: 2.1.50
• OS: Windows 10 Pro (Build 19045)
• Terminal: Windows Terminal
• Platform: Anthropic API