hive.deepseek IAddon: runs the SSE bridge (hive-vessel.executor.sse), owns
the vessel registry, and
presents on behalf of every dependency that offers a presenter seat.

Config (manifest :addon/config merged with runtime config):
  :deepseek/port          bridge port (default 7925, 0 = any)
  :deepseek/host          bind host (default loopback)
  :deepseek/token         shared secret the dsh plugin must send
  :deepseek/presenter-id  id registered on presenter seats (default :deepseek)

Registry: hive-vessel's standard translators, then the `:vessel/translators`
hook of every injected dependency, then translators added at runtime
through the `:vessel/register-translators!` hook.

Presenter seats: a dependency whose hooks include a key named
`register-presenter!` (hive.carto-flow's is one) gets this vessel's
delivery registered under the presenter id, so its frames reach dsh with no
code on either side naming the other.

DeepSeek Harness as a hive vessel.

The vessel speaks hive-vessel's :json dialect; its executor is hive-vessel's
SSE bridge, consumed by the dsh browser plugin (dsh/ in this repo), which
paints panels in the right Sidebar, raises notices, opens workspace files
and re-emits `json/event` messages as Cordis events.

Two faces over the same target:
- `target`     -- a hive-vessel target, for plan / dispatch! / broadcast!
- `->vessel`   -- a hive-addon IVessel, for a host's vessel registry; its
                  :delivery capability accepts ops or presentation
                  envelopes and dispatches them through the registry.