feat(bridge): protocol 12 — BetterChat and popups (phase 17)

- titles.set: a whole set of chat titles, swapped in by reference and read
  by a BetterChat third-party title getter (one lookup, no socket). The
  getter is registered at load and again whenever BetterChat loads.
- perm.sync: a group may carry its BetterChat style. Each field is written
  through API_SetGroupField only when the game still holds what the site
  last pushed (or BetterChat's default); anything else is reported as
  drift. One `chat group set` per touched group saves it, because the API
  never does (D143). A retired style removes the group with `chat group
  remove` (D139). The report gains `chat`.
- chat.say: delivery chat|popup and an optional voice format. A popup with
  PopupNotifications absent is refused `popup-unavailable`. Every line said
  is logged, since the game logs neither a broadcast nor a popup.
- server.hello/status carry `integrations`; `rg.titles [steamId]` prints
  what BetterChat would render for a player.
- overlay.toml: protocol 12; PopupNotifications leaves requires_plugins
  (D141).

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

overlay.toml

@@ -26,12 +26,13 @@
 # the same change that alters the emitters, exactly as the sidecar bumps
 # PROTOCOL_VERSION and the module bumps its own constant.
 #
-# Current: 10 — the transport, the read path, identity, the permission mirror,
+# Current: 12 — the transport, the read path, identity, the permission mirror,
 # configuration from the site, first-party clans, a raid frame that names who
 # lives there, the event leases, the world verbs events place and give back, and
 # the rewards: a run's participation tally, kit credits and chat (PROTOCOL.md §16),
-# and the map: its picture and everything that moves on it (PROTOCOL.md §17).
-protocol = 11
+# the map: its picture and everything that moves on it (PROTOCOL.md §17), and the
+# optional mods: BetterChat titles and group styles, and popups (PROTOCOL.md §18).
+protocol = 12
 
 # ── Oxide compatibility ──────────────────────────────────────────────────────
 #
@@ -54,5 +55,9 @@ min_oxide_version = "2.0.7585"
 # The uMod **Clans** plugin is deliberately NOT listed (docs/modules/rust/PLAN.md
 # D47). Teams come from Rust's own clan system, which that plugin never touches,
 # so requiring it would split a server's players across two unrelated clan
-# systems. It belongs to phase 17's optional tier.
-requires_plugins = ["Kits", "PopupNotifications", "ZoneManager"]
+# systems. Phase 17 dropped the adapter it was meant to get (D134).
+#
+# **PopupNotifications is not listed either** (D141). It is optional: a popup
+# asked of a server without it is refused with a reason, and chat is the default.
+# BetterChat is optional in the same way — titles and group styles wait for it.
+requires_plugins = ["Kits", "ZoneManager"]