Remote Control mobile/desktop view: show currently running subagents (live agent roster)

**Feature request.** In a Remote Control session viewed from mobile (or desktop web), there is no way to see which subagents are currently running.

**Today:** the main session spawns agents (Agent tool / background tasks) and the RC view only shows their side effects — completion notifications and idle pings interleaved into the conversation. From a phone you cannot answer: how many agents are live right now, what is each one doing, and how long has it been running. The terminal has `/tasks` and the inline task tree; RC has no equivalent.

**Ask:** a lightweight "agents" panel (or pinned status row) in the RC mobile/desktop view listing live subagents and background tasks: name, one-line description, state (running / idle / done), started-at. Tapping one could show its latest output snippet.

**Why it matters:** supervising multi-agent work is the main reason to check a session from a phone. Pairing this with #87951 (collapse the injected teammate-message wrappers) would turn the mobile RC view from a boilerplate scroll into an actual supervision surface: quiet conversation + a live agent roster.

**Environment:** Claude Code Remote Control, iOS app + desktop web, 2026-08-19.

Review the Remote Control mobile and desktop views, then compare their current behavior with the /tasks command and inline task tree. Done means the view provides a live roster for subagents and background tasks with each requested field—name, description, state, and start time—and optionally a latest output snippet.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.