Agent tool `isolation: "worktree"` is silently ignored when spawning teammates with `team_name`

Summary

When spawning a teammate via the Agent tool with a team_name, the isolation: "worktree" parameter is silently ignored. The teammate runs in the main working directory on the main branch instead of an isolated git worktree. The same isolation: "worktree" parameter works correctly for non-team background agents (no team_name).

Environment

• Claude Code version: 2.1.172 (@anthropic-ai/claude-code@2.1.172)
• Platform: Linux (Ubuntu container)

Expected behavior

A teammate spawned with isolation: "worktree" should automatically start inside an isolated git worktree (e.g. .claude/worktrees/<name> on branch worktree-<name>), the same way non-team background agents do.

Actual behavior

The teammate starts in the main working directory (/workspace/test) on the main branch (master). The isolation parameter has no effect — it is a silent no-op on the team spawn path.

Reproduction

Controlled comparison, varying only team_name:

| # | Spawn method | isolation | Called EnterWorktree? | Landing spot | Isolated? |
|---|---|---|---|---|---|
| 1 | Team teammate (team_name set) | worktree | no | /workspace/test @ master | ❌ |
| 2 | Team teammate (team_name set) | worktree | no | /workspace/test @ master | ❌ |
| 3 | Non-team background agent | worktree | no | .claude/worktrees/agent-<id> @ worktree-agent-<id> | ✅ |
| 4 | Team teammate | — | yes (manual) | .claude/worktrees/worktree-test-2 | ✅ |
| 5 | Team teammate (team_name set) | worktree | no | /workspace/test @ master | ❌ |

Steps:

1. Create a team with TeamCreate.
2. Spawn a teammate via the Agent tool with team_name, name, and isolation: "worktree".
3. In the teammate, run pwd, git branch --show-current, git rev-parse --show-toplevel.
4. Observe the teammate is in the main working dir on the main branch, not in an isolated worktree.
5. For contrast, spawn a background agent without team_name but with isolation: "worktree" — it correctly lands in .claude/worktrees/agent-<id>.

The only differing variable between the working and broken cases is the presence of team_name.

Workaround

Have the team teammate explicitly call the EnterWorktree tool at the start of its task (case #4 above), then verify with pwd / git branch --show-current before making changes.