Give the Team tab sub-sections of its own

The Team tab was five cards stacked on one page: the rota, the escalation
ladder, the alert sources, the dead man's switches and the membership.
07914d5 split the Admin tab for three reasons, and all three were sharper
here. There was no way to link somebody to the escalation ladder, which is
the thing a team owner most often has to be talked through. There was no
way to the switches but scrolling past a month of rota -- and the rota
became a month grid in v0.18.0, which made the page taller rather than
shorter. And the poll loop refetched six endpoints every tick however
little of the page you were looking at.

Each is now a route: /team/rota, /team/members, /team/escalation,
/team/sources, /team/deadman, reached from the same strip of links the
Admin tab uses, with /team an overview. A page fetches only what it shows,
so the switches are one GET and the sources are one, where every tick used
to be six.

Three of the five fetch the member list besides their own endpoint, and
for the same reason each time: a rota entry, a ladder target and a role are
all a person, and the page has to be able to name them. The overview is the
one that fetches everything, because saying how much of each there is means
asking each of them -- who is on call today, how many members and owners,
how many ladder levels and whether a fallback follows them, how many keys
and how many never used, how many switches. That is what it is for; a strip
that already links to the five does not need a second menu that repeats it.

team.js owns the table of its six routes, as admin.js owns its four, and
app.js parses against both rather than keeping a third list to drift from
them. The table carries a title beside the label where the strip's word is
too thin to name a page on its own: "Sources" is a fine tab and a poor
browser tab, so that page titles as Alert sources and the switches keep
their apostrophe in the top bar.

menuItem left admin.js for ui.js as menuCard, since both tabs now open on
one, and its CSS went from .admin-menu* to .overview-*. That is the rename
.user-link -> .row-link was in v0.18.0, for the same reason: the class was
named after the first page that used it rather than after what it is.

The read-only notice a member sees is now on the overview only. It explains
why the controls further down are missing, and a page that is nothing but
the rota grid has no controls to explain. The team picker sits above the
strip, because it changes the subject of all five, and it drops the ladder
draft when it moves -- an unsaved edit belongs to the team it was started
in.

No server change. Extensionless paths already fall back to index.html, so
/team/rota survives a reload the way /admin/users/{id} does, and no
endpoint, payload or permission moved.

Nobody has looked at this in a browser, the caveat 07914d5 and a6fa673
carried. What is checked is the wiring, and rather more of it than last
time: every sub-page was rendered against a stub fetch and a pocket DOM,
each with exactly one aria-current and fetching only the endpoints named
above; and app.js itself was booted the same way and walked through all
seventeen URLs the app has, which resolve to one section each with the
right title -- the six new ones, the four Admin ones, both subject pages,
and /incidents/42 and /nonsense still falling to the queue. Whether six
entries scroll cleanly at phone width is not checked.

Claude-Session: https://claude.ai/code/session_01RHPj4ggeFdEjKKfm4SHbD7

README.md

@@ -85,11 +85,16 @@ How a browser stays signed in:
 With `TERDUT_PUBLIC_URL` set, tapping a push notification opens the incident in
 the web UI (`/incidents/{id}`).
 
-A **Team** tab holds everything a team owns: the on-call rota, the escalation
-ladder, the alert sources with their keys, the dead man's switches and the
-membership. An owner edits it; a member sees the same page read-only, because
-the server refuses their writes anyway. Somebody in more than one team picks
-between them at the top.
+A **Team** tab holds everything a team owns, in five sub-sections with a URL
+each and a strip across the top to move between them: the on-call rota
+(`/team/rota`), the membership (`/team/members`), the escalation ladder
+(`/team/escalation`), the alert sources with their keys (`/team/sources`) and
+the dead man's switches (`/team/deadman`). `/team` itself is an overview — who
+is on call today, how many members and owners, how many ladder levels, how many
+keys and how many switches — so a page fetches only what it shows. An owner
+edits it; a member sees the same pages read-only, because the server refuses
+their writes anyway. Somebody in more than one team picks between them above
+the strip, since the choice changes the subject of all five.
 
 The rota is a month at a time, one coloured initial per day with a legend
 underneath, and it says how many days are left uncovered — the question a rota