[FEATURE] Agents view: mark the main session, and use color to keep parallel work legible in the terminal

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

The agents view lists the main session, background agents, and worktree-isolated jobs as identical rows. Nothing marks which one is the main session.

With 6-8 agents running, it's easy to lose track of which context is primary. The risk isn't cosmetic: main and worktree agents have different working trees, so acting on the wrong one means edits land in a worktree that gets discarded, or worktree changes get committed as if they were main's. Both fail silently — nothing errors, the work just ends up in the wrong place.

At higher concurrency the view is also an undifferentiated wall of text: no visual signal for running vs finished vs failed, or worktree vs in-place.

Proposed Solution

Mark the main session unmistakably — a "main" badge, a pin, or first position with distinct styling.

Plus:

• Distinguish worktree-isolated agents from in-place ones (they carry the divergence risk, and look identical today).
• Show each agent's branch/worktree path on its row.
• Use color as an organizing signal: main vs spawned, worktree vs in-place, running vs finished vs failed.

The terminal has precision but loses legibility as concurrency rises; the desktop app is legible but gives up micro-level control. Colored, clearly-differentiated rows close that gap.

Alternative Solutions

Currently I track the primary session mentally and re-check git status / the worktree path before acting on an agent's output. That's after-the-fact verification, not prevention — and since the failure is silent, by the time you check the work may already be in the wrong tree.

Priority

Medium - Would be very helpful

Feature Category

Interactive mode (TUI)

Use Case Example

1. A task fans out 6 scouts plus an architect isolated in its own git worktree.
2. The agents view fills with 7 identically-styled rows plus my main session.
3. An agent finishes and I want to act on its result.
4. Nothing on screen shows which row is the session I'm typing into, or which agents worked in a separate tree.
5. A "main" badge plus color coding would answer both at a glance — before acting, not after.

Additional Context

The main session already knows it's the main session, and worktree isolation is explicit at spawn time — so this looks like a display change rather than new state tracking.