[Feature Request] A native dashboard that loads and monitors the task list across sessions and background agents — not just one session's `/tasks`

Problem

Today, the only built-in way to see task status is typing /tasks inside a single session — and that only shows that one session's own task list. There's no native way to see, at a glance, the state of everything actually running: multiple sessions, background agents, and whatever they've each completed, are stuck on, or have silently finished without anyone noticing.

That gap is real enough that I ended up hand-building my own monitoring dashboard just to get basic visibility into a fleet of agents working in parallel — wiring a local server, a custom UI, and endpoints just to answer "what's actually done, what's actually running, and what silently finished without telling me." That's a lot of infrastructure to build just to get a status board.

It also runs into a class of bug that a native, first-party monitor could catch far better than a hand-rolled one: agents that have genuinely finished but still show as active in the session view, and background tasks that complete silently with no reliable signal, requiring a manual sweep to even discover the output exists. Both of those are documented in detail, with reproductions, here: #76987.

Proposed solution

A native dashboard — could be a TUI panel, a persistent local web view, or a desktop-app tab — that:

• Loads and monitors task lists across all active sessions and background agents, not just the one you're currently attached to.
• Reflects genuinely reliable completion state — a task shown as "done" should mean done, and a task that's actually finished shouldn't still read as active because the display didn't get the memo.
• Requires no custom wiring to get basic visibility — this should be something that works the moment you have more than one agent running, not something you build yourself.

Related, not a duplicate

#73963 asks for a sidebar showing one session's own task list without typing /tasks — a good, narrower version of part of this. This request is the broader, cross-session/cross-agent monitoring layer that #73963's single-session panel would sit inside of.