Spawn was `s`/`S` in the TUI and `n`/`N` in the web client; the TUI now
uses `n`/`N` too. The web sidebar gains `c`, `r` and `x` — collapse,
rename, kill — which the TUI already bound.
docs/SIDEBAR.md now carries the shared table, so a new binding has one
place to land on both clients.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
