(remote): a live remote session with no transcript yet is invisible and cannot be stopped

[devsuitup]

Symptom

Observed 2026-09-12 on v0.0.76 (and unchanged by #274): a remote CLI launched in tmux on the host writes its descriptor ~/.claude/sessions/<pid>.json at once, but no transcript until the first prompt is sent. The remote inventory (LIST_COMMAND in remote-transport.js) lists .jsonl and .meta.json files only, so the session has no row in the sidebar until it has been prompted once — a manual host refresh does not help. Measured: launched 00:47, invisible until a first prompt at 00:50 created -srv-echanges-switchboard-test/934a8ba5-….jsonl.

Why it matters

Since #272 a remote row is the only place to stop a remote process, and since #267 a listed descriptor means "alive". A running CLI that never got a prompt is a live process nobody can see or stop from the app — the same class of gap as #271.

Fix

Let the inventory report live descriptors that have no transcript yet (the descriptor carries cwd, pid, status, tmux), and let remote-index.js synthesize a placeholder session for them: project from cwd, id = the descriptor's session id if present else pid:<n>, liveness: alive, no transcript; the row is attachable and stoppable, shows the status/age, and is replaced by the real session once its .jsonl appears (same id, so no duplicate row). Mirror nothing for it.

Acceptance

• A descriptor with no transcript yields one row within one poll; the row attaches and stops like any other.
• When the transcript appears, the row is the same row (no duplicate, no flicker) — test on the id mapping.
• A dead pid's descriptor (ALIVE:0) still yields nothing.
• Mutation dropping the placeholder synthesis makes the first test red.