fix(rust): nothing names who is online by default

The org lead's rule, settled 2026-09-22: who is online is always the
narrowest audience - staff - unless an operator deliberately widens it,
and a count is fine where a list of names is not.

The public site broke that in three places since phase 4. The Online
tab named every player, the feed carried joins, respawns, deaths, chat
and tallies, and the leaderboard's lastSeen - refreshed every minute by
a gather tally - said who was on as plainly as either. All three now
sit behind one setting:

* PRESENCE_KINDS, a subset of the public allowlist, gated per request.
  Below the audience the feed keeps the server's own story (wipe, start,
  shutdown) and says presenceHidden rather than looking quiet.
* the Online route answers { players: [], hidden, count, audience } -
  same shape, so an older client renders empty rather than breaking.
* rungs staff / signed_in / public, fleet-wide default in a new
  rust_settings table with an optional per-server override on
  rust_servers; an unknown stored word narrows to staff.
* the viewer's standing is RE-READ from the users row (ctx.users.getById),
  not taken from the token, so a demotion or a ban applies on the next
  request. Walked: a moderator demoted mid-session lost the roll call on
  the same cookie.
* per-viewer answers are Cache-Control: private, no-store.
* GET/PUT /admin/rust/visibility (requireRole admin) and an admin page,
  Rust visibility; every save is one activity-log row.

The browser walk also found every empty state in this module rendering
as a blank box. Core's EmptyState renders children only; this module
passed title/message (the shape the Integration Kit template teaches)
and React dropped both without a word. Fixed module-side with a small
Empty wrapper - nothing core or module-uo renders changes - and a client
test that refuses a titled EmptyState or a PageHeader subtitle.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

server/db/schema.sql

@@ -668,3 +668,36 @@ CREATE TABLE IF NOT EXISTS rust_config_writes (
     FOREIGN KEY (user_id) REFERENCES users (id) ON DELETE SET NULL,
   KEY idx_rust_config_writes_server (server_id, created_at)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+
+
+-- ── Who may see who is online (the presence fix, 2026-09-22) ──────────────
+--
+-- The org lead's rule: **nothing tells who is online by default.** The Online
+-- list, the killfeed, chat and every other frame that says a named player was on
+-- the server reach STAFF unless an operator deliberately widens them. A count is
+-- not a name and stays public.
+--
+-- Two places, because the decision has two shapes:
+--
+--   • `rust_settings` holds the FLEET default — one row per key. A key/value
+--     table rather than a column per setting, because phase 9's clan-roster
+--     audience is the next key and a table that grows a column per setting grows
+--     an ALTER per setting.
+--   • `rust_servers.presence_audience` is an optional PER-SERVER override. NULL
+--     means "inherit the fleet default", which is not the same as any audience —
+--     an operator who later narrows the fleet must narrow every server that never
+--     chose otherwise.
+--
+-- The stored value is a word (`staff` · `signed_in` · `public`) and an unknown
+-- word reads as `staff` (`model/visibility`): a typo in a row must narrow, never
+-- widen.
+CREATE TABLE IF NOT EXISTS rust_settings (
+  setting_key  VARCHAR(64)   NOT NULL PRIMARY KEY,
+  value        VARCHAR(255)  NOT NULL,
+  updated_by   INT           NULL,
+  updated_at   DATETIME      NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  CONSTRAINT fk_rust_settings_user
+    FOREIGN KEY (updated_by) REFERENCES users (id) ON DELETE SET NULL
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+
+ALTER TABLE rust_servers ADD COLUMN IF NOT EXISTS presence_audience VARCHAR(16) NULL;