Retire the Ink TUI client (and trim its server-side surface)

[pskeshu]

Splitting this out of #100 rather than doing it mid-session on the rig.

What prompted it

While reading the new process console during a production session, the agent log
appeared to be full of TUI activity:

gently.ui.web.routes.agent_ws INFO agent_websocket:985 TUI client disconnected

That was misleading, not evidence. The line fired on every agent-websocket
disconnect, including ordinary browser tabs. Already relabelled in #100 — but it
prompted the real question: is the TUI still carrying its weight?

What is actually dead

gently/tui/ — an Ink/TypeScript client, 35 files, 244 KB.

Nothing in the Python tree imports it. grep -rn "from gently.tui\|gently\.tui"
over gently/ and launch_gently.py returns zero hits. It is not launched, not
packaged, and not referenced by the desktop shell. Outside its own directory it
appears only in prose: docs/guides/hardware-setup.md and
notes/biologist-readiness-plan.md.

What is NOT dead — do not delete this

gently/ui/web/routes/agent_ws.py is live and shared. The browser agent panel
and the TUI connect to the same endpoint:

• gently/ui/web/static/js/agent-chat.js:1090 → new WebSocket(.../ws/agent)
• gently/tui/src/index.tsx:27 → ws://localhost:8080/ws/agent

agent-chat.js:4 says so outright: "Connects to the same /ws/agent bridge the
TUI uses." So /ws/agent stays. This is why it is not a delete-the-folder job,
and why the naming throughout that module ("Send a JSON message to the TUI
client", "Tell TUI we're entering wizard mode") is now actively misleading — it
describes the browser.

The trimmable delta

The server handles 8 message types; the browser sends 6. The gap is the
candidate TUI-only surface:

msg_type	browser sends	notes
chat, command, cancel, choice_response, take_control, pong	yes	shared — keep
browse	no	agent_ws.py:1041 — "Handle browse requests from the TUI browser panel"
ping	no	browser answers pings, never initiates one

Verify before cutting: browse may have a non-TUI caller (mesh peer? a future
panel?), and ping may be worth keeping as a generic liveness affordance even
with no current sender.

Proposed work

1. Delete gently/tui/ and its package.json / package-lock.json.
2. Remove the TUI references from docs/guides/hardware-setup.md and
   notes/biologist-readiness-plan.md.
3. Confirm browse has no remaining caller; remove the handler and
   handle_browse_request if so.
4. Decide on ping — keep as generic liveness, or drop.
5. Rename the TUI-era vocabulary in agent_ws.py to say "agent client", since
   the browser is now the only one.

Why not now

The only consumer that matters (the browser agent panel) runs through this
module continuously during a live session. Cutting handlers out of it while a
sample is mounted is not worth the risk for a 244 KB saving. After Ryan's first
session is the right time.

Found while preparing #100.