[Feature]: Mobile — show the environment prominently on a new task, and allow color-coding environments #8479

Summary

Two related gaps around environment visibility on mobile:

1. When starting a new task from the phone app, there is no environment selector on the first message the way there is on desktop/web — and the environment isn't shown prominently either, so you can't tell which machine you're about to run on.
2. There's no way to tell environments apart at a glance anywhere in the mobile UI. Color-coding (even as an opt-in) would make the "Choose project" and active-sessions lists readable instantly.

1. No environment selector / indicator on the first message (mobile)

On desktop/web you pick the environment as part of composing the first message of a task. On the phone app that selector isn't there — you go through Choose project and the environment is implied by whichever project entry you tap.

That's workable if the environment is obvious, but it isn't: the project list shows the project name and the absolute path, and nothing about which environment the entry belongs to.

Concretely, in my "Choose project" list I have a project group with three workspaces, all rendered as:

monorepo
/home/<me>/git/monorepo
/home/<me>/git/monorepo
/home/<me>/git/monorepo

Three identical rows. They are three different environments on (or pointing at) the same path, and the list gives me no way to know which is which — I have to guess, tap one, and find out after the fact.

Ask: either bring the first-message environment selector to mobile as well, or (cheaper) show the environment name prominently on each project row and on the composer for a new task, so the destination is unambiguous before I send.

Related: #5623 covers naming environments (they all default to the hostname). Even with good names, mobile currently doesn't surface the name where it matters — so these two together are what make the list unusable.

2. Color-code environments (at least as an option)

Right now, looking at the active sessions list, you can't see:

• whether several sessions are running on the same host, or
• whether a host is idle / has nothing running on it.

A per-environment colour — assigned automatically with an option to override, or purely opt-in — applied as an accent/dot/left border on project rows, session rows, and the composer would answer both of those at a glance, without adding text to already-dense rows.

This feels like a cheap win: it's the same information already in the model, just made scannable.

Environment

• Android phone app