Feature request: show git worktree in the agent list (claude agents / FleetView)

## Feature request

The interactive agent list screen (reached via the left arrow, and backed by `claude agents`) lists all running sessions as rows, but doesn't surface which git worktree each session is running in.

This info already exists — `claude agents --json` includes a `cwd` field per session that reflects the worktree path — but it's not rendered anywhere in the interactive list view, and there's no settings option to add it.

## Use case

I often have several background sessions running in parallel across different worktrees of the same repo (e.g. `expanded-player-redesign`, `audio-player-refactor`). In the agent list, rows are hard to tell apart at a glance because the worktree/branch isn't shown — I have to cross-reference with `claude agents --json` to know which session is working where.

## Request

Add the worktree (or at minance the branch name / directory name) as a visible field per row in the agent list screen, ideally as a small customization option (e.g. a settings.json toggle) since not everyone runs multiple worktrees.

## What I checked

- `~/.claude/settings.json` schema (including the `worktree: {...}` config block for symlinkDirectories/sparsePaths/baseRef/bgIsolation/location) — no display/column customization keys exist there.
- `claude agents --help` and `claude --help` — no relevant flags.
- `claude agents --json` — confirms the underlying data (`cwd`) is already tracked per session, just not displayed in the TUI.

Start with the interactive agent list reached via the left arrow and compare its rows with the data returned by `claude agents --json`, especially each session's `cwd` field. Review `~/.claude/settings.json` and the existing `claude agents` help output to determine whether the display should be configurable; done means the agent list clearly identifies each session's worktree, branch, or directory.

Written by the indexing model from the issue text.