The TUI read its leader from `[tui].leader`; the web used `DEFAULT_LEADER`,
a module constant. Rebinding one left the other on `ctrl-a`, so the two
escape hatches hanging off the leader (`leader ctrl-k`, `leader leader`)
moved on one client and not the other.
`GET /api/info` now carries `leader`. The web binds that when it arrives and
rebuilds the leader-owning `CommandSet`, so the `?` overlay and the command
bar render the configured chord; an absent or empty field — an older daemon,
or an unreachable `/api/info` — leaves it on `ctrl-a`.
Chose the existing `[tui].leader` served as-is over a new shared key: one
knob, no precedence rules between two spellings, and no migration for
operators who already set it. The name is a wart — it is the leader for every
client now, not the TUI's — and `docs/COMMAND-BAR.md` and `docs/INSTALL.md`
say so.