isolation: "worktree" silently fails when combined with team_name parameter

Description

When using isolation: "worktree" together with team_name on an Agent call (agent teams feature via CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1), the worktree creation silently fails. Agents land in the main working directory instead of an isolated worktree. No error is raised — the agent proceeds as if no isolation was requested.

Reproduction

1. Enable agent teams: "CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS": "1" in settings
2. Create a team via TeamCreate
3. Spawn an agent with both team_name and isolation: "worktree":

``
Agent(
name: "worker",
team_name: "my-team",
isolation: "worktree",
run_in_background: true,
prompt: "Run git rev-parse --show-toplevel and report the result"
)
``

1. The agent reports the main repo root, not a worktree path

Expected behavior

The agent should run in a temporary git worktree (a separate directory), and git rev-parse --show-toplevel should return the worktree path, not the main repo root.

Actual behavior

git rev-parse --show-toplevel returns the main project root. The agent is in the main working directory with no isolation.

Impact

• All 3 agents dispatched in a single session hit this — it's 100% reproducible, not intermittent
• Without the worktree, parallel agents editing the same repo can cause conflicts
• Workaround: verify file disjointness upfront and allow agents to proceed in the main directory, but this defeats the purpose of isolation

Environment

• macOS (Darwin 25.3.0)
• Claude Code with CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1
• Model: Claude Opus 4.6

Workaround

Add a "worktree check" to agent prompts (git rev-parse --show-toplevel) so agents detect the failure immediately. If agents are file-disjoint, the lead can override and allow them to proceed in the main directory.