[FEATURE] Remote access to sessions should be the default, not opt-in per session

This is constructive criticism from someone who uses Claude Code daily and prefers it for the actual work.

The use case: I kick off a long-running task on my Mac — a build, a multi-step refactor, an agent working through a task list — and then I walk away from my computer. Life happens; I'm in another room, or out of the house entirely.

The problem: if I didn't proactively run the remote-control command before standing up, that session is stranded on my desktop. There's no way to check on it, answer a question it's blocked on, or steer it from my phone. The one moment I need remote access is precisely the moment I can no longer enable it — I'm not at the machine anymore.

The comparison that stings: with ChatGPT, I don't have to set anything up. If something is running when I walk away, it's just there on my phone — same conversation, same state, no ceremony. The session being reachable from anywhere is the default, not a feature I have to remember to invoke per-session.

What I'd like: make desktop sessions reachable from my phone retroactively — either remote access on by default for my own authenticated devices (with an opt-out for people who don't want it), or at minimum let the mobile app see and attach to sessions running on my trusted machines. If there's already a setting that does this, it's not discoverable enough that a daily user found it.

Opt-in-per-session is the wrong default for a tool whose whole promise is autonomous work that continues while I'm not watching. The agent doesn't need me sitting there — but the session access model assumes I am.

Related: #77985 (machine-level remote control) addresses session-death survival; this request is about retroactive/default reachability of sessions that were started without remote control enabled.